Aqueous polyester coating compositions

ABSTRACT

An aqueous coating composition comprising a crosslinkable water-dispersible polyester oligomer wherein said composition when drying to form a coating has the following properties: an open time of at least 20 minutes, a wet edge time of at least 10 minutes, a thumb hard time of ≦48 hours and a tack-free time ≦20 hours and an equilibrium viscosity of ≦5000 Pa.s at any solids content when drying in the range of from 20 to 55 wt % using a shear rate in the range of from 9±0.5 to 90±5 s −1  and at 23±2° C.

The present invention relates to certain aqueous ambient temperaturecrosslinkable and shelf stable polyester polymer compositions which,inter alia, provide coatings having improved open and wet edge times aswell as good tack-free times.

A general need when applying a decorative or protective coating to asubstrate is to be able to repair irregularities in the still-wetcoating after some time has elapsed, for example by re-brushing over afreshly coated wet substrate, or by applying more of the coatingcomposition over a previously coated substrate either over the main areaof the coating or an edge of the coating or even blending a drop intothe coating without vitiating the complete merging of any boundaries inthe vicinity of the repaired irregularity. Traditionally compositionscontaining binder polymers dissolved in organic solvents are used andthe organic solvents are employed to modify the drying characteristicsof the coated composition. For example, organic solvent based alkydswith an open time of 30 to 45 minutes are available in the decorative“Do-it-yourself” DIY market. However the disadvantage of organic solventbased coatings is the toxic and flammable nature of such solvents andthe pollution and odour caused on evaporation as well as the relativelyhigh cost of organic solvents.

Thus with the continuing concern about the use of organic solvent basedcoating compositions there has been a long felt need for an aqueouscoating composition with comparable properties to those achievable usingorganic solvent based compositions.

Unfortunately, aqueous polymer coating compositions currently known tothe art do not offer a combination of drying properties which would makethem fully comparable (or even superior to) solvent-based coatings, andin particular do not provide desirably long open and wet edge times (asdiscussed above and also later) together with desirably short tack-freetimes (discussed later).

Thus, very commonly, aqueous-based polymer coating compositions employdispersed high molecular weight polymers as the binder materialsthereof. This results in, inter alia, a short wet edge time when thecoating composition is dried because the dispersed polymer particlestend to coalesce in the edge region of an applied coating very soonafter a wet coating has been applied (probably due to the maximumpacking fraction of the polymer particles having been reached) to form acontinuous film, and since the polymer of this film is of high viscositybecause of its high molecular weight, the lapping (i.e. wet edge) timeof the composition is poor.

It has been shown by viscosity measurements taken during drying thatexisting alkyd emulsions have a high viscosity phase inversion peakduring drying. (Phase inversion is defined as the transition from abinder in a continuous water phase to water in a continuous binder phasewhich occurs during drying). The consequence is a difficulty inre-brushing which starts a few minutes after application of the coating.

It is known from the prior art that longer wet edge or open time isachievable by using solution-type aqueous oligomers (U.S. Pat. No.4,552,908) which can be diluted with large amounts of organic solvent(s)in order to create a low viscosity continuous phase during drying of thefilm. However, these systems have high Volatile Organic Contents (VOC's)and are generally unacceptably water-sensitive.

Open time can also be prolonged by using evaporation suppressants (suchas e.g. eicosanol), as described in for example EP 210747. However,water sensitivity is also a problem in this case. Moreover, the wet edgeopen time is insufficiently improved by using such evaporationsuppressants.

From the literature it is also known that open time is easily prolongedby using low solids contents in the aqueous polymer compositions, butthis generally results in the need to apply many layers of paint (forgood opacity). In addition, the wet edge time is generally onlymoderately influenced by reducing the solids content of an aqueouscoating composition with water.

Longer times for repairing irregularities can be achieved by employingaqueous coating compositions in which the binder polymers have very lowviscosities. However, hitherto, a problem with such low viscositypolymer binders, is that the resultant coatings have a slow drying rate,resulting in the coating remaining tacky for an unacceptably long time.A coating should also preferably dry sufficiently quickly to avoid theadherence of dust and to ensure that the coating quickly becomeswaterproof (in case of outdoor applications), and as discussed abovequickly becomes tack-free and sufficiently hard.

Indeed, the difficulty in developing aqueous polymer coatingcompositions having a desirable combination of drying properties whencoated onto a substrate has been particularly discussed in a recentinterview given by Professor Rob van der Linde (Professor of CoatingsTechnology, University of Technology, Eindhoven, NL) and Kees van derKolk (Sigma Coatings) and reported in “Intermediair” 10.06.1999, 35(23),pages 27–29. In this interview, concerning environmentally friendlypaints, there is described the problem of applying aqueous paints whereeven the professional painter has little enough time to correct anyirregularities when needed. This is contrasted (in the interview) withsolvent-based paints (e.g. alkyd paints) which are workable for a muchlonger time but have the disadvantage that the organic solvents, forminga major component of such compositions, are toxic and expensive. Theinterview also mentions that in the coming years, three universitieswill cooperate in a project to overcome the drying disadvantages ofaqueous paints. Thus this interview emphasises the current andcontinuing need and desirability for achieving aqueous polymer coatingscompositions having improved drying properties.

The open time for a coating composition is, in brief, the period of timethat the main area (the bulk) of an applied aqueous coating remainsworkable after it has been applied to a substrate, in the sense thatduring this period re-brushing or application of more coating over themain area of a freshly coated wet substrate is possible without causingdefects such as brush marks in the final dried coating. (A more formaldefinition of open time is provided later in this specification).

The wet edge time for a coating composition is the period of time thatthe edge region of an applied aqueous coating remains workable after ithas been applied to a substrate, in the sense that during this periodre-brushing or application of more coating over the edge region of afreshly coated wet substrate is possible without causing defects such aslap lines in the final dried coating. (A more formal definition of wetedge time is provided later in this specification).

U.S. Pat. No.4,552,908 describes a solids/viscosity relationship ofoligomers with defined molecular weight upon drying coatings appliedfrom compositions containing the oligomers. The compositions have >10minutes wet edge time, but there is no mention that the oligomers arecrosslinkable (an important feature of the present invention—see later).All oligomers mentioned in the patent are very water-sensitive.

WO 97/26303 discloses a water-borne hybrid composition comprising anemulsifiable resin, an aqueous polymer dispersion and surfactant wherethe composition has a dry solids content of 60 to 90% by weight. Howeverno drying properties are exemplified or described.

WO 00/24837 discloses a polyurethane/acrylate dispersion blended with apolyurethane with oxidatively drying groups; however the maximum opentime was only 7 minutes, and, in particular, a wet edge time of only 4minutes was achieved, neither of which is sufficient for most decorativepurposes.

U.S. Pat. No.4,346,044 discloses water-soluble air drying alkyds,however a high solvent content is required and no drying properties areexemplified.

We have now invented aqueous polymer coating compositions having a veryadvantageous combination of drying properties, particularly with regardto open time and tack-free time as discussed above, and which(surprisingly in view of the comments by van der Linde and van der Kolk)avoid the drawbacks of the currently available compositions.

According to the present invention there is provided an aqueous coatingcomposition comprising a crosslinkable water-dispersible polyesteroligomer(s) wherein said composition when drying to form a coating hasthe following properties:

-   -   i) an open time of at least 20 minutes;    -   ii) a wet-edge time of at least 10 minutes;    -   iii) a thumb hard time of ≦48 hours;    -   iv) a tack-free time of ≦20 hours;    -   v) 0 to 25% of co-solvent by weight of the composition; and    -   vi) an equilibrium viscosity of ≦5,000 Pa.s, at any solids        content when drying in the range of from 20 to 55% by weight of        the composition, using any shear rate in the range of from 9±0.5        s⁻¹ to 90±5 s⁻¹ and at 23±2° C.

Open time is more formally defined as the maximum length of time, usingthe test method, under the specified conditions described herein, inwhich a brush carrying the aqueous composition of the invention can beapplied to the main area of a coating of the aqueous composition of theinvention after which the coating flows back so as to result in ahomogenous film layer.

Preferably the open time is at least 25 minutes, more preferably atleast 30 minutes and most preferably at least 35 minutes.

Wet edge time is more formally defined as the maximum length of time,using the test method, under the specified conditions described herein,in which a brush carrying the aqueous composition of the invention canbe applied to the edge region of a coating of the aqueous composition ofthe invention after which the coating flows back without leaving any laplines so as to result in a homogenous film layer.

Preferably the wet-edge time is at least 12 minutes, more preferably atleast 15 minutes and especially at least 25 minutes.

The drying process can be divided in four stages namely the period oftime necessary to achieve dust-free, tack-free, sandable and thumb-hardcoatings using the tests described herein.

Preferably the dust free time is ≦4 hours, more preferably ≦2 hours andmost preferably ≦50 minutes.

Preferably the tack-free time is ≦15 hours, preferably ≦12 hours, morepreferably ≦10 hours and most preferably ≦8 hours.

Preferably the thumb hard time is ≦24 hours, most preferably ≦16 hoursand especially ≦10 hours.

Preferably the resultant coating is sandable within 72 hours, morepreferably within 48 hours, still more preferably within 24 hours, andespecially within 16 hours.

A co-solvent as is well known in the coating art, is an organic solventemployed in an aqueous composition to improve the drying characteristicsthereof.

The co-solvent may be solvent incorporated or used during preparation ofthe polyester oligomer(s) or may have been added during formulation ofthe aqueous composition.

The equilibrium viscosity of the aqueous coating composition whenmeasured under the conditions as described above, is a suitable methodfor illustrating the drying characteristics of the aqueous coatingcomposition. By the equilibrium viscosity of an aqueous composition at aparticular shear rate and solids content is meant the viscosity measuredwhen the aqueous composition has been subjected to the shear rate at forlong enough to ensure that the viscosity measurement has reached aconstant value.

If the composition is to remain brushable and workable during drying sothat it has the desired open time and wet edge time, it is necessarythat its equilibrium viscosity does not exceed defined limits during thedrying process and hence over a range of solids contents. Accordinglythe crosslinkable water-dispersible polyester oligomer(s) which are usedin this invention do not give a significant phase inversion viscositypeak, if any at all, during the drying process when the system invertsfrom one in which water is the continuous phase to one in which thecrosslinkable water-dispersible polyester oligomer(s) is the continuousphase.

The shear rate to measure the equilibrium viscosity is preferably anyshear rate in the range of from 0.9±0.05 to 90±5 s⁻¹, more preferablyany shear rate in the range of from 0.09±0.005 to 90±5 s⁻¹.

Preferably the equilibrium viscosity of the aqueous coating compositionof the invention is ≦3000 Pa.s, more preferably ≦1500 Pa.s, still morepreferably ≦500 Pa.s, especially ≦100 Pa.s and most especially ≦50 Pa.swhen measured as defined above.

Preferably, the composition of the invention has an equilibriumviscosity ≦5,000 Pa.s when measured using any shear rate in the range offrom 0.09±0.005 to 90±5 s⁻¹, and an equilibrium viscosity of ≦3,000 Pa.swhen measured using any shear rate in the is range of from 0.9±0.05 to90±5 s⁻¹, and an equilibrium viscosity of ≦1,500 Pa.s when measuredusing any shear rate in the range of from 9±0.5 to 90±5 s⁻¹, at anysolids content when drying in the range of from 20 to 55% by weight ofthe composition and at 23±2° C.

More preferably, the composition of the invention has an equilibriumviscosity of ≦3,000 Pa.s when measured using any shear rate in the rangeof from 0.09±0.005 to 90±5 s⁻¹, and an equilibrium viscosity of ≦1,500Pa.s when measured using any shear rate in the range of from 0.9±0.05 to90±5 s³¹ ¹, and an equilibrium viscosity of ≦500 Pa.s when measuredusing any shear rate in the range of from 9±0.5 to 90±5 s⁻¹, at anysolids content when drying in the range of from 20 to 55% by weight ofthe composition and at 23±2° C.

Most preferably, the composition of the invention has an equilibriumviscosity of ≦1500 Pa.s when measured using any shear rate in the rangeof from 0.09±0.005 to 90±5 s⁻¹, and an equilibrium viscosity of ≦200Pa.s when measured using any shear rate in the range of from 0.9±0.05 to90±5 s⁻¹, and an equilibrium viscosity of ≦100 Pa.s when measured usingany shear rate in the range of from 9±0.5 to 90±5 s⁻¹, at any solidscontent when drying in the range of from 20 to 55% by weight of thecomposition and at 23±2° C.

Preferably the equilibrium viscosity of the composition of the inventionis ≦5000 Pa.s, more preferably ≦3000 Pa.s when measured using any shearrate in the range of from 0.9±0.05 to 90±5 s⁻¹, more preferably usingany shear rate in the range of from 0.09±0.005 to 90±5 s³¹ ¹, after a12%, preferably a 15% and most preferably a 18% increase in the solidscontent by weight of the composition.

A 12% increase in the solids content by weight of the composition meansfor example going from a solids content of 35 to 47% by weight of thecomposition.

Preferably the solids content of the aqueous coating composition whendetermining the equilibrium viscosity is in the range of from 20 to 60%,more preferably in the range of from 20 to 65%, most preferably in therange of from 20 to 70%, especially in the range of from 20 to 75%.

In a preferred embodiment of the present invention said polyesteroligomer(s) has a solution viscosity ≦150 Pa.s, as determined from a 80%by weight solids solution of the crosslinkable polyester oligomer(s) inat least one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof, at a shear rateof 90±5 s⁻¹ and at 50±2° C.

A choice of solvents for determining the solution viscosity of thepolyester oligomer(s) is provided herein because the nature of thepolyester oligomer(s) may affect their solubility.

Preferably the solution viscosity of the crosslinkable polyesteroligomer(s) is ≦100 Pa.s, more especially ≦50 Pa.s and most especially≦20 Pa.s when measured as defined above.

Alternatively, and more preferably, the solution viscosity of thepolyester oligomer(s) may be measured at 23±2° C. and the crosslinkablepolyester oligomer(s) may thus also be described as preferably having asolution viscosity ≦250 Pa.s, as determined from a 70% by weight solidssolution of the crosslinkable polyester oligomer(s) in a solvent mixtureconsisting of:

i) at least one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof;

ii) water and

iii) N,N-dimethylethanolamine;

where i), ii) and iii) are in weight ratios of 20/7/3 respectively,using a shear rate of 90±5 s⁻¹ and at 23±2° C.

Preferably in the preceding alternative the solution viscosity of thecrosslinkable polyester oligomer(s) is ≦100 Pa.s, more especially ≦50Pa.s and most especially ≦20 Pa.s when measured as defined herein at23±2° C.

If a mixture of N-methylpyrrolidone (NMP) and n-butylglycol (BG) isused, preferably the ratio of NMP:BG is in the range of from 0.01:99.9to 99.9:0.01, more preferably the ratio of NMP:BG is in the range offrom 0.01:99.9 to 10:90 and in the range of from 90:10 to 99.9:0.01, andmost preferably the ratio of NMP:BG is in the range of from 0.5:99.5 to5:95 and in the range of from 95:5 to 99.5:0.5.

In a special embodiment of the present invention the wet edge time inminutes of the aqueous coating composition is at least Q/(wt. % solidsof the aqueous coating composition)^(0.5), wherein the solids content ofthe aqueous coating composition is between 15 and 70 wt. %, morepreferably between 30 and 65 wt. % and most preferably between 40 and 60wt. % and Q is a constant of 84, more preferably of 100, most preferablyof 126 and especially of 151.

The crosslinkable polyester oligomer(s) may crosslink at ambienttemperature by a number of mechanisms including but not limited toautoxidation, Schiff base crosslinking and silane condensation. Bycrosslinking by autoxidation is meant that crosslinking results from aoxidation occurring in the presence of air and usually involves a freeradical mechanism and is preferably metal-catalysed resulting incovalent crosslinks. By Schiff base crosslinking is meant thatcrosslinking takes place by the reaction of a carbonyl functionalgroup(s), where by a carbonyl functional group herein is mean an aldo orketo group and including an enolic carbonyl group such as is found in anacetoacetyl group, with a carbonyl-reactive amine and/or hydrazine (orblocked amine and/or blocked hydrazine) functional group. Examples ofcarbonyl-reactive amine (or blocked amine) functional groups includeones provided by the following compounds or groups: R—NH₂, R—O—NH₂,R—O—N═C<, R—NH—C(═O)—O—N═C< and R—NH—C(═O)—O—NH₂ where R is optionallysubstituted C₁ to C₁₅, preferably C₁ to C₁₀ alkylene, optionallysubstituted alicyclic or optionally substituted aryl, or R may also bepart of a polymer. Examples of carbonyl-reactive hydrazine (or blockedhydrazine) compounds or groups include R—NH—NH₂, R—C(═O)—NH—NH₂,R—C(═O)—NH—N═C<, R—NH—C(═O)—NH—NH₂ and R—NH—C(═O)—NH—N═C< where R is asdescribed above. By silane condensation is meant the reaction of alkoxysilane or —SiOH groups in the presence of water, to give siloxane bondsby the elimination of water and/or alkanols (for example methanol)during the drying of the aqueous coating composition.

Preferably the crosslinkable polyester oligomer(s) is aself-crosslinkable polyester oligomer(s) (i.e. crosslinkable without therequirement for added compounds which react with groups on the polyesteroligomer(s) to achieve crosslinking, although these can still beemployed if desired). Preferably the crosslinking is by autoxidation,optionally in combination with other crosslinking mechanisms asdiscussed herein. Suitably autoxidation is provided for example by fattyacid groups containing unsaturated bonds (by which is meant the residueof such fatty acids which have become incorporated into the polyesteroligomer(s) by reaction with their carboxyl groups) or by (meth)allylfunctional residues, β-keto ester groups or β-keto amide groups.Preferably autoxidation is provided at least by fatty acid groupscontaining unsaturated bonds.

Preferably the concentration of unsaturated fatty acid groups if presentin the autoxidisably crosslinkable polyester oligomer(s) is 10 to 80%,more preferably 12 to 70%, most preferably 15 to 60% by weight based onthe weight of the polyester oligomer(s). If combined with otherautoxidisable groups in the aqueous coating composition, the fatty acidcontent may be below 10% by weight of the polyester oligomer(s). For thepurpose of determining the fatty acid group content of the polyesteroligomer(s), it is convenient for practical purposes to use the weightof the fatty acid reactant including the carbonyl group but excludingthe hydroxyl group of the terminal acid group of the fatty acid.Suitable unsaturated fatty acids for providing fatty acid groups in theoligomer(s) include fatty acids derived from vegetable oil andnon-vegetable oil such as soyabean oil, palm oil, linseed oil, tung oil,rapeseed oil, sunflower oil, tallow oil, (dehydrated) castor oil,safflower oil and fatty acids such as linoleic acid, linolenic acid,palmitoleic acid, oleic acid, eleostearic acid, licanic acid,arachidonic acid, ricinoleic acid, erucic acid, gadoleic acid,clupanadonic acid and/or combinations thereof. Particularly preferred isa polyester oligomer(s) in which the autoxidisable groups are onlyderived from unsaturated fatty acids. Preferably at least 40% by weight,more preferably at least 60% by weight, of the unsaturated fatty acidgroups contain at least two unsaturated groups.

Other crosslinking mechanisms known in the art include the reaction ofepoxy groups with amino, carboxylic acid or mercapto groups, thereaction of amine or mercapto groups with ethylenically unsaturatedgroups such as fumarate and acryloyl groups, the reaction of maskedepoxy groups with amino or mercapto groups, the reaction ofisothiocyanates with amines, alcohols or hydrazines, the reaction ofamines (for example ethylene diamine or multifunctional amine terminatedpolyalkylene oxides) with -diketo (for example acetoacetoxy oracetoamide) groups to form enamines. The use of blocked crosslinkinggroups may be beneficial.

The crosslinkable polyester oligomer(s) may be completely water-soluble(which is less preferred) or only have partial solubility in water. Ifthe crosslinkable polyester oligomer(s) is only partially soluble thecrosslinkable polyester oligomer(s) preferably has low water solubilityin a pH range of from 2 to 10 and is either self-water-dispersible (i.e.dispersible by virtue of a sufficient concentration of selected bound(in-chain, chain-pendant and/or chain-terminal) hydrophilic groups builtinto the crosslinkable polyester oligomer(s), and thus not requiringhigh shear techniques and/or added surfactants to produce thedispersion, although such methods can also be included if desired), oris only dispersible in water with the aid of added (i.e. external)surface active agents and/or use of high shear mixing. Low watersolubility confers the advantage of a reduced water-sensitivity of theapplied coating to water. Such low water solubility is defined herein asthe crosslinkable polyester oligomer(s) being less than 80% by weightsoluble in water throughout the pH range of from 2 to 10 as determinedby a centrifuge test as described herein. Preferably the crosslinkablepolyester oligomer(s) is ≦50% most preferably ≦30% by weight soluble inwater throughout the pH range of from 2 to 10.

The crosslinkable polyester oligomer(s) preferably contains a sufficientconcentration of bound hydrophilic water-dispersing groups capable ofrendering the oligomer self water-dispersible, but the concentration ofsuch groups is preferably not so great that the oligomer has anunacceptably high water solubility in order to not compromise the watersensitivity of the final coating.

The type of hydrophilic groups capable of rendering the crosslinkablepolyester oligomer(s) water-dispersible are well known in the art, andcan be ionic water-dispersing groups or non-ionic water-dispersinggroups. Preferred non-ionic water-dispersing groups are polyalkyleneoxide groups, more preferably polyethylene oxide groups. A small segmentof the polyethylene oxide group can be replaced by propylene oxidesegment(s) and/or butylene oxide segment(s), however the polyethyleneoxide group should still contain ethylene oxide as a major component.When the water-dispersible group is polyethylene oxide, the preferredethylene oxide chain length is >4 ethylene oxide units, preferably >8ethylene oxide units and most preferably >15 ethylene oxide units.Preferably the polyester oligomer(s) have a polyethylene oxide contentof 0 to 50% by weight, more preferably 0 to 45% by weight, still morepreferably 0 to 38% by weight, especially 3 to 35% by weight and mostpreferably 5 to 25% by weight. Preferably the polyethylene oxide grouphas a Mw from 175 to 5000 Daltons, more preferably from 350 to 2200Daltons , most preferably from 660 to 2200 Daltons.

Preferred ionic water-dispersing groups are anionic water-dispersinggroups, especially carboxylic, phosphonic and or sulphonic acid groups.The anionic water-dispersing groups are preferably fully or partially inthe form of a salt. Conversion to the salt form is optionally effectedby neutralisation of the crosslinkable polyester oligomer(s) with abase, preferably during the preparation of the crosslinkable polyesteroligomer(s) and/or during the preparation of the composition of thepresent invention. The anionic dispersing groups may in some cases beprovided by the use of a monomer having an already neutralised acidgroup in the polyester oligomer(s) synthesis so that subsequentneutralisation is unnecessary. If anionic water-dispersing groups areused in combination with a non-ionic water-dispersing group,neutralisation may not be required.

If the anionic water-dispersing groups are neutralised, the base used toneutralise the groups is preferably ammonia, an amine or an inorganicbase. Suitable amines include tertiary amines, for example triethylamineor N,N-dimethylethanolamine. Suitable inorganic bases include alkalihydroxides and carbonates, for example lithium hydroxide, sodiumhydroxide, or potassium hydroxide. A quaternary ammonium hydroxide, forexample N⁺(CH₃)₄OH⁻, can also be used. Generally a base is used whichgives the required counter ion desired for the composition. For example,preferred counter ions include Li⁺, Na⁺, K⁺, NH₄ ⁺ and substitutedammonium salts.

Cationic water dispersible groups can also be used, but are lesspreferred. Examples include pyridine groups, imidazole groups and orquaternary ammonium groups which may be neutralised or permanentlyionised (for example with dimethylsulphate).

The crosslinkable polyester oligomer(s) preferably has a weight averagemolecular weight (Mw) in the range of from 1000 to 100,000 Daltons,preferably in the range of from 1000 to 80,000 Daltons, more preferablyin the range of from 1000 to 50,000 Daltons, most preferably in therange of from 1000 to 20,000 Daltons. For the purpose of this inventionany molecular species mentioned herein with a Mw <1000 Daltons isclassified as either a reactive diluent or a plasticiser and istherefore not taken into account for the determination of the Mw, Mn andPDi. When Daltons are used to give molecular weight data, it should beunderstood that this is not a true molecular weight but a molecularweight measured against polystyrene standards.

Preferably a significant part of any crosslinking reaction only takesplace after application of the aqueous coating composition to asubstrate, to avoid an excessive molecular weight build up which maylead to an increased viscosity of the aqueous coating composition on thesubstrate in the early stages of drying.

The molecular weight limits suitable to obtain the preferred lowsolution viscosity of the crosslinkable polyester oligomer(s) as definedabove may depend in part on the amount and type of co-solvent present inthe aqueous composition of the invention, where a higher molecularweight limit is possible when there is more co-solvent in thecomposition, and the lower molecular weight preferences are moreapplicable to low or zero co-solvent concentrations.

The molecular weight distribution (MWD) of the crosslinkable polyesteroligomer(s) has an influence on the equilibrium viscosity of the aqueouscomposition of the invention and hence an influence on the open time.MWD is conventionally described by the polydispersity index (PDi). PDiis defined as the weight average molecular weight divided by the numberaverage molecular weight (Mw/Mn) where lower values are equivalent tolower PDi's. It has been found that a lower PDi often results in lowerviscosities for a given Mw crosslinkable polyester oligomer(s).Preferably the value of PDi is ≦30, more preferably ≦15, still morepreferably ≦10 and most preferably ≦5. In a preferred embodiment thevalue of Mw×Pdi^(0.8) of the crosslinkable polyester oligomer(s) is≦550,000, more preferably the Mw×PDi^(0.8) is ≦400,000, still morepreferably the Mw×PDi^(0.8) is ≦300,000 and most preferably theMw×PDi^(0.8) is ≦220,000.

The crosslinkable polyester oligomer(s) may comprise a singlecrosslinkable polyester oligomer(s) or a mixture of polyesteroligomer(s). The crosslinkable polyester oligomer(s) may optionally beused in conjunction with crosslinkable oligomer(s) of a non-polyestertype which has a solution viscosity within the same preferred limits asthe solution viscosity of the polyester oligomer(s). Indeed up to 90% byweight of crosslinkable oligomers in the invention composition may be ofa non-polyester type. The crosslinkable oligomer(s) (polyester typeplus, if present, non-polyester type) may optionally be used inconjunction with up to 250% by weight thereof of any type ofnon-crosslinkable oligomer (i.e. polyester and/or non-polyester type)provided that the non-crosslinkable oligomer(s) has a solution viscositywithin the preferred ranges defined above (for the crosslinkablepolyester oligomer(s)). In such cases, more preferably up to 120 wt. %of the non-crosslinkable oligomer(s) (based on the weight ofcrosslinkable oligomer(s) is used, still more preferably up to 70 wt. %,especially up to 30 wt. %, more especially up to 10 wt. %, and mostpreferably 0%. Oligomer(s) of a non polyester type include but are notlimited to for example vinyl oligomer(s), polyamide oligomer(s),polyether oligomer(s), polycarbonate oligomer(s), polysiloxaneoligomer(s) and/or polyurethane oligomer(s) and the non-polyester typeoligomer(s) may optionally be branched.

The crosslinkable polyester oligomer(s) can be prepared usingconventional polymerisation procedures known to be effective forpolyester synthesis. General processes for the preparation of alkydpolyesters are described in “Alkyd Resin Technology” by T C Patton,Publisher John Wiley & sons Inc. (1962). General methods for preparingcrosslinkable polyesters are also disclosed in EP 486092, U.S. Pat. Nos.3,494,882, 4,251,406, EP 0000087, WO 95/02019, U.S. Pat. No. 5,378,757and GB 2306489. Thus, it is well known that polyesters, which containcarbonyloxy (i.e. —C(═O)—O—) linking groups may be prepared by acondensation polymerisation process in which monomer(s) providing an“acid component” (including ester-forming derivatives thereof) isreacted with monomer(s) providing a “hydroxyl component”. The monomer(s)providing an acid component may be is selected from one or morepolybasic carboxylic acids such as di- or tri-carboxylic acids orester-forming derivatives thereof such as acid halides, anhydrides oresters. The monomer(s) providing a hydroxyl component may be one or morepolyhydric alcohols or phenols (polyols) such as diols, triols, etc.Mono-functional acid and hydroxy components may also be included in thepreparation of the crosslinkable polyester oligomer(s). (It is to beunderstood, however, that the polyester oligomer(s) may contain, ifdesired, a proportion of carbonylamino linking groups —C(=O)—NH— (i.e.amide linking group) by including an appropriate amino functionalreactant as part of the “hydroxyl component” or alternatively all of thehydroxyl component may comprise amino functional reactants, thusresulting in a polyamide oligomer; such amide linkages are in factuseful in that they are more hydrolysis resistant.) The reaction to forma polyester oligomer(s) may be conducted in one or more stages (as iswell known). It would also be possible to introduce in-chainunsaturation into the polyester oligomer(s) by e.g. employing as part ofthe monomer(s) providing an acid component an olefinically unsaturateddicarboxylic acid or anhydride.

There are many examples of carboxylic acids (or their ester formingderivatives) which can be used in polyester oligomer(s) synthesis forthe provision of the monomer(s) providing an acid component. Examplesinclude, but are not limited to monofunctional acids such as (alkylated)benzoic acid and hexanoic acid; and C₄ to C₂₀ aliphatic, alicyclic andaromatic dicarboxylic acids (or higher functionality acids) or theirester-forming derivatives (such as anhydrides, acid chlorides, or loweralkyl esters). Specific examples include adipic acid, fumaric acid,maleic acid, succinic acid, itaconic acid, azeleic acid, sebacic acid,nonanedioic acid, decanedioic acid, 1,4-cyclohexanedicarboxylic acid,1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid,terephthalic acid, fatty acid dimers, isophthalic acid, 5-sodiosulphoisophthalic acid, phthalic acid and tetrahydrophthalic acid. Anhydridesinclude succinic, maleic, phthalic, trimellitic and hexahydrophthalicanhydrides.

Similarly there are many examples of polyols which may be used inpolyester oligomer(s) synthesis for the provision of the monomer(s)providing a hydroxyl component. The polyol(s) preferably have from 1 to6 (more preferably 2 to 4) hydroxyl groups per molecule. Suitablemonofunctional alcohols include for example eicosanol and laurylalcohol. Suitable polyols with two hydroxy groups per molecule includediols such as 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol,1,6-hexanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), the1,2-, 1,3- and 1,4-cyclohexanediols and the corresponding cyclohexanedimethanols, diethylene glycol, dipropylene glycol, and diols such asalkoxylated bisphenol A products, e.g. ethoxylated or propoxylatedbisphenol A. Suitable polyols with three hydroxy groups per moleculeinclude triols such as trimethylolpropane (TMP) and 1,1,1-tris(hydroxymethyl)ethane (TME). Suitable polyols with four or more hydroxygroups per molecule include bis-TMP, pentaerythritol(2,2-bis(hydroxymethyl)-1,3-propanediol), bis-pentaerythritol andsorbitol (1,2,3,4,5,6-hexahydroxyhexane).

The crosslinker groups may be introduced into the polyester oligomer(s)using two general methods: i) by utilising in the polymerisation processto form a polyester oligomer(s) monomer(s) providing at least part ofthe acid or hydroxyl components which carry a crosslinker group; or ii)utilising monomer(s) providing at least part of the acid or hydroxylcomponents which bears selected reactive groups and which monomer(s) issubsequently reacted with a compound carrying a crosslinker group andalso a reactive group of the type which will react with the selectedreactive groups on the monomer to provide attachment of the crosslinkergroup to the polyester oligomer(s) via covalent bonding.

To prepare autoxidisably crosslinkable polyester oligomer(s) preferablya monomer providing an acid or a hydroxyl component bearing anunsaturated fatty acid group(s) as crosslinker group(s) may be used inthe polyester oligomer(s) synthesis.

Hydrophilic water-dispersing groups (or groups which may be subsequentlyconverted to such water-dispersing groups) are optionally introducedinto the polyester oligomer(s) using two general methods: i) byutilising in the polymerisation process to form a polyester oligomer(s)monomer(s) providing part of the acid or hydroxyl component which carrya hydrophilic water-dispersing group; or ii) utilising monomer(s)providing part of the acid or a hydroxyl component which bears selectedreactive groups and which monomer is subsequently reacted with acompound carrying a hydrophilic water-dispersing group and also areactive group of the type which will react with the selected reactivegroups on the monomer to provide attachment of the hydrophilicwater-dispersing group to the polyester oligomer(s) via covalentbonding.

The hydrophilic water-dispersing groups if present, should be present insufficient level in the polyester oligomer(s) to impartwater-dispersibility thereto. Suitable non-ionic hydrophilic waterdispersing groups include for example ethylene oxide-containing hydroxyfunctional compounds such as alkoxypolyethlene glycols and polyethyleneglycols. Preferably the hydrophilic water-dispersing groups arecarboxylic acid groups, sulphonic acid groups or sulphonate anion groups(neutralisation of the sulphonic acid groups preferably already havingbeen effected in the monomer). Preferably incorporation of carboxylicacid groups can occur by having a residual carboxylic acidfunctionality, post functionalisation of hydroxy-functionalisedpolyester oligomer(s) or use of sterically hindered hydroxy functionalacids such as dimethylolpropionic acid. Preferably, the sulphonic acidor sulphonate anion containing monomer is a dicarboxylic acid monomerhaving at least one sulphonic acid salt group substituent.Alternatively, alkyl ester groups may be used in place of the carboxylicacid groups. Such a monomer will therefore be part of the acid componentused in the polyester synthesis. Examples of such compounds are thealkali metal salts of sulphonic acid substituted aromatic dicarboxylicacids, for example alkali metal salts of 5-sulpho-1,3-benzenedicarboxylic acid. Particularly preferred is sodio-5-sulphoisophthalicacid (SSIPA). Other useful sulphonic acid containing monomers are thealkali metal salts of sulphonic acid substituted aromatic dicarboxylicacid-dihydroxyalkylesters such as the alkali metal salts of5-sulpho-1,3-benzenedicarboxylic acid-1,3-bis(2-hydroxyethyl)ester.

Preferably the ionic sulphonate water-dispersing group content of thepolyester oligomer(s) is in the range of from 7.5 to 100milliequivalents of ionic water-dispersing groups per 100 g of polyesteroligomer(s), more preferably from 10 to 75 milliequivalents per 100 g.Preferably the acid value of the polyester oligomer(s) is in the rangeof from 0 to 150 mgKOH/g, more preferably in the range of from 0 to 120mgKOH/g, especially in the range of from 5 to 90 mgKOH/g, moreespecially in the range of from 10 to 60 mgKOH/g and most especially inthe range of from 10 to 40 mgKOH/g.

If the polyester oligomer(s) is prepared using monomer(s) providing acidor hydroxyl component which have an unsaturated group(s), the polyesteroligomer(s) will have un-saturation incorporated into its structure, andcan if desired be subjected to a further stage of polymerisation by afree radical mechanism, to cause chain-extension of the polyester andsuch a reaction would usually take place in an aqueous dispersion phase,rather than in the melt as when conducting the esterificationpolymerisation process. Alternatively the unsaturated group in thepolyester oligomer(s) may be utilised to provide further functionalgroups, for example by reaction with an aminosilane, whereby the aminogroups add to the double bonds via a Michael addition reaction, so as tointroduce alkoxy silane functionality of the polyester oligomer(s). Anyresidual unsaturation may also be utilised for reaction with any fattyacid unsaturation.

Suitable monomers providing an acid component and an unsaturated groupinclude but are not limited to fumaric acid, maleic acid, maleicanhydride and hydroxyalkyl(meth)acrylates, for examplehydroxyethylmethacrylate.

The esterification polymerisation processes for making the polyesteroligomer(s) for use in the invention composition are well known in theart and need not be described here in detail. Suffice to say that theyare normally carried out in the melt using catalysts such as tin-basedcatalysts and with the provision for removing any water (or alcohol)formed from the condensation reaction.

An organic solvent may optionally be added before or after thepolymerisation process to control the viscosity. Examples of solventsinclude water-miscible solvents such as N-methylpyrrolidone, glycolethers such as butyldiglycol, diglyme and alkyl ethers of glycolacetates or mixtures of N-methylpyrrolidone and methyl ethyl ketone.Optionally no organic solvents are added.

The polyester oligomer(s) may be dispersed in water using techniqueswell known in the art. An aqueous dispersion of the polyesteroligomer(s) may be readily prepared by adding water directly to the hotpolyester oligomer(s) melt until the desired solids content/viscosity isreached. Alternatively the polyester oligomer(s) may be dispersed inwater by adding an aqueous pre-dispersion (or organic solvent solution)of the polyester oligomer(s)to the water phase. Still further an aqueousdispersion may be prepared by dispersion of the solidified melt from thecondensation polymerisation directly into water. The solidified melt ispreferably in a form such as flake (which can often be obtained directlyfrom the melt) or comminuted solid (obtained for example by grinding).

The polyester oligomer(s) normally do not require the use of an externalsurfactant when being dispersed into water, although surfactants and orhigh shear can be utilised in order to assist in the dispersion of thepolyester oligomer(s) in water (even if it is self-dispersible).Suitable surfactants include but are not limited to conventionalanionic, cationic and/or non-ionic surfactants such as Na, K and NH₄salts of dialkylsulphosuccinates, Na, K and NH₄ salts of sulphated oils,Na, K and NH₄ salts of alkyl sulphonic acids, Na, K and NH₄ alkylsulphates, alkali metal salts of sulphonic acids; fatty alcohols,ethoxylated fatty acids and/or fatty amides, and Na, K and NH₄ salts offatty acids such as Na stearate and Na oleate. Other anionic surfactantsinclude alkyl or (alk)aryl groups linked to sulphonic acid groups,sulphuric acid half ester groups (linked in turn to polyglycol ethergroups), phosphonic acid groups, phosphoric acid analogues andphosphates or carboxylic acid groups. Cationic surfactants include alkylor (alk)aryl groups linked to quaternary ammonium salt groups. Non-ionicsurfactants include polyglycol ether compounds and polyethylene oxidecompounds. The amount used is preferably 0 to 15% by weight, morepreferably 0 to 8% by weight, still more preferably 0 to 5% by weight,especially 0.1 to 3% by weight and most especially 0.3 to 2% by weightbased on the weight of the crosslinkable polyester oligomer(s).

The aqueous dispersion of the polyester oligomer(s) may be for example,a colloidal dispersion of the polyester oligomer(s) in water (i.e. anemulsion or latex) or a solution (molecular dispersion) of the polyesteroligomer(s) in water, or a combination thereof.

The glass transition temperature (Tg) of the polyester oligomer(s) mayvary within a wide range. The Tg (as measured by modulated differentialscanning calorimetry) is preferably in the range of from −90 to 100° C.,more preferably −90 to 50° C. especially −75 to 30° C. and mostpreferably −60 to 10° C.

The aqueous composition of the invention may optionally but preferablyinclude a polymer dispersed therein which is not a polyester oligomer(or a non-polyester oligomer whether crosslinkable or non-crosslinkable)and has a Mw≧120,000 Daltons, (herein termed a dispersed polymer forconvenience). Preferably the weight average molecular weight of thedispersed polymer(s) in the aqueous polymer dispersion is in the rangeof from 120,000 to 6,000,000, more preferably in the range of from150,000 to 2,000,000, and especially in the range of from 250,000 to1,500,000. If the dispersed polymer(s) is fully pre-crosslinked its Mwwill be infinite. Also, in some cases, the synthesis to form thecrosslinkable polyester oligomer(s) yields, in addition to the polyesteroligomer(s), an amount of very high molecular material. For the purposesof this invention, such material, produced in-situ, is to be consideredas a dispersed polymer. The Mw of the dispersed polymer(s) may be<120,000 Daltons with the proviso that the solution viscosity of thedispersed polymer(s) is >150 Pa.s as determined from a 80% by weightsolids solution of the dispersed polymer(s) in at least one of thesolvents selected from the group consisting of N-methyl pyrrolidone,n-butyl glycol and mixtures thereof using a shear rate of 90±5 s⁻¹ andat 50±2° C.

Preferably the solution viscosity (if measurable) of the dispersedpolymer(s) when used in the aqueous composition of the invention is ≧250Pa.s more preferably ≧500 Pa.s and especially ≧1000 Pa.s, as determinedfrom an 80% by weight solids solution of the dispersed polymer(s) in atleast one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof, using a shearrate of 90±5 s⁻¹ and at 50±2° C.

The solution viscosity of the dispersed polymer(s) may not be measurableif for example the weight average molecular weight is so high, so as torender the dispersed polymer(s) insoluble or if the dispersed polymer(s)is fully or partially crosslinked, again rendering the dispersedpolymer(s) insoluble.

The dispersed polymer(s) may be film forming or non-film forming atambient temperature, preferably the dispersed polymer(s) is non-filmforming at ambient temperature (ambient temperature as used herein isdefined as 23±2° C). Preferably the aqueous composition of the inventiondoes include such a dispersed polymer(s).

The crosslinkable polyester oligomer(s) can thus be (and preferably is)combined with a dispersed polymer(s) to further improve the provision ofa binder system for providing an aqueous composition with the desiredbalance of long open/wet edge time and reduced tack free time.

The presence of the crosslinkable polyester oligomer(s) (as discussedabove) provides the defined long open time and wet edge time, whilst thepresence of the dispersed polymer(s) (e.g. a polymer latex) appears toassist in reducing the drying time of the composition, even though itspresence may not be essential to achieve the defined requirements inthis respect.

Accordingly in a further, and preferred, embodiment of the presentinvention there is provided an aqueous coating composition as definedherein additionally comprising a dispersed polymer(s). The dispersedpolymer(s) may for example be the product of an aqueous emulsionpolymerisation or a preformed polymer dispersed in water.

Preferably the dispersed polymer(s) has a Tg measured using DSC, whichis in the range of from −50 to 300° C., more preferably in the range offrom 25 to 200° C. and most preferably in the range of from 35 to 125°C. If the dispersed polymer(s) is a vinyl polymer, the vinyl polymer maybe a sequential polymer, i.e. the vinyl polymer will have more than oneTg. Especially preferred is a vinyl polymer with 10 to 50 wt. % of asoft part with a Tg in the range of from −30 to 20° C. and 50 to 90 wt.% of a hard part of with a Tg in the range of from 60 to 110° C. Thiscombination provides an additional advantage of improved blockresistance of the resultant coating, especially when co-solvent levelsof 0 to 15 wt. %, more preferably 0 to 5 wt. % and most preferably 0 to3 wt. %. of the aqueous composition are used. A simple blend ofdispersed polymers with high and low Tg's may also be used to achievethe same or similar advantage. Blocking is the well-known phenomenon ofcoated substrates which are in contact tending to unacceptably adhere toeach other, particularly when under pressure, as for example in doorsand windows in their respective frames or when stacked.

Preferably the dispersed polymer(s) has an average particle size in therange of from 25 to 1000 nm, more preferably 60 to 700 nm, mostpreferably 100 to 600 nm and especially in the range of from 175 to 500nm. The dispersed polymer may also have a polymodal particle sizedistribution.

The dispersed polymer(s) preferably has a low solubility in the aqueousmedium of the composition of the invention, however some of thedispersed polymer(s) may be soluble measurable by the centrifuge test asdescribed herein. Preferably at least 30%, more preferably at least 60%,most preferably at least 90% and especially at least 94% by weight ofthe dispersed polymer(s) is present as insoluble polymer over the wholepH range.

The dispersed polymer(s) may for example be vinyl polymer, polyester,polyamide, polyepoxide, or a mixture thereof. The dispersed polymer(s)may also be a hybrid of two or more different polymer types such asurethane-acrylic polymers (as described in for example U.S. Pat.No.5,137,961), epoxy-acrylic polymers and polyester-acrylic polymers.The dispersed polymer(s) may also be an organic-inorganic hybrid, forexample silica particles grafted with a vinyl polymer(s). Preferably thedispersed polymer(s) is a vinyl polymer. Blends of dispersed polymersmay of course also be used.

The dispersed polymer(s) may optionally contain carboxylic acid groups.The dispersed polymer(s) preferably has an acid value below 150 mgKOH/g,more preferably an acid value in the range from 3 to 120 mg/KOH/g, mostpreferably an acid value in the range from 4 to 180 mg KOH/g, especiallyan acid value in the range from 5 to 30 mg KOH/g and most especially anacid value in the range from 6 to 19 mgKOH/g. The preferred acid valueof the dispersed polymer(s) depend on the nature of the crosslinkablepolyester oligomer(s) and the amount of co-solvent in the aqueouscomposition of the invention. If the oligomer is hydrophilic, theco-solvent if used is preferably also of a hydrophilic nature and a lowacid value of the dispersed polymer(s) is preferred (preferably below60, more preferably below 40, most preferably below 24, and especiallybelow 15 mg KOH/g). If however a hydrophobic oligomer is used, forinstance based on (at least partly) unsaturated fatty acid and withoutdispersing groups, the cosolvent is preferentially of a hydrophobicnature (if at all present) and therefore much higher acid values (up toan acid value of 160, more preferred up to 125, most preferred up to 100mg KOH/g) of the dispersed polymer(s) may be tolerated to give thedesired properties.

In a special embodiment, ≦15 wt. % of a co-solvent (based on totalbinder solids where the binder includes the oligomer(s) and anydispersed polymer(s)) is used, where the dispersed polymer(s) has anacid value below 20 mg KOH/g and the crosslinkable polyester oligomer(s)is present in an amount (based on total binder polymer solids) of 35 to65 wt. %, the crosslinkable polyester oligomer comprising 45 to 70 wt. %of fatty acid groups.

The dispersed polymer(s) may optionally contain hydroxyl groups. If thedispersed polymer(s) is a vinyl polymer comprising polymerised(meth)acrylic monomers then preferably the hydroxyl group content in thevinyl polymer is preferably below 1.0 wt. %, more preferably below 0.5wt. % and most preferably below 0.2 wt. % based on the weight of thevinyl polymer.

The dispersed polymer(s) may optionally contain amide groups (such asgroups being for example obtainable from amide functional monomers suchas (meth)acrylamide).

If the dispersed polymer(s) is a vinyl polymer comprising polymerised(meth)acrylamide monomers, then preferably the amide group content inthe vinyl polymer is below 3.0 wt. %, more preferably below 1.5 wt. %and most preferably below 0.6 wt. % based on the weight of the vinylpolymer.

The dispersed polymer(s) may optionally contain wet-adhesion promotinggroups such as acetoacetoxy groups; (optionally substituted) amine orurea groups, for example cyclic ureido groups, imidazole groups,pyridine groups, hydrazide or semicarbazide groups.

The dispersed polymer(s) may optionally contain crosslinker groups whichallow crosslinking of the dispersed polymer(s) and/or allowparticipation in the crosslinking reaction of the crosslinkablepolyester oligomer(s), thus speeding up the drying rate and improvingthe properties of the final coating (e.g. chemical resistance andscratch resistance). Examples of such crosslinker groups include groupswhich can take part in the autoxidation and groups which will effectcrosslinking other than by autoxidation, for example, Schiff base andsilane condensation reactions as discussed above for polyesteroligomer(s).

In a preferred embodiment the dispersed polymer(s) contains crosslinkergroups which can participate in the preferred autoxidative crosslinkingreactions of an autoxidisably crosslinkable polyester oligomer(s).

In a preferred embodiment the dispersed polymer(s) may be partially orfully pre-crosslinked. If the dispersed polymer(s) is a vinyl polymerpre-crosslinking may be achieved by using polyunsaturated monomersduring the vinyl polymer synthesis such as allyl methacrylate, diallylphthalate, tripropylene glycol di(meth)acrylate, 1,4-butanedioldiacrylate and trimethylol propane triacrylate (TMPTA). Allylmethacrylate is most preferred. Alternatively very low levels ofinitiator may be used, leading to chain-transfer to the vinyl polymerand hence to grafting and high Mw. Other ways to generatepre-crosslinking in a vinyl polymer is to include the use of monomer(s)bearing groups which may react with each other during synthesis toeffect pre-crosslinking for example glycidylmethacrylate and acrylicacid.

Vinyl polymer(s) are derived from free radically polymerisableolefinically unsaturated monomers (vinyl monomers) and can containpolymerised units of a wide range of such vinyl monomers, especiallythose commonly used to make binders for the coatings industry.

Examples of vinyl monomers which may be used to form vinyl polymer(s)include but are not limited to 1,3-butadiene, isoprene, styrene,ic-methyl styrene, divinyl benzene, acrylonitrile, methacrylonitrile,vinyl halides such as vinyl chloride, vinylidene halides such asvinylidene chloride, vinyl esters such as vinyl acetate, vinylpropionate, vinyl laurate, and vinyl esters of versatic acid such asVeoVa 9 and VeoVa 10 (VeoVa is a trademark of Shell), heterocyclic vinylcompounds, alkyl esters of mono-olefinically unsaturated dicarboxylicacids (such as di-n-butyl maleate and di-n-butyl fumarate) and, inparticular, esters of acrylic acid and methacrylic acid of formulaCH₂═CR¹—COOR²wherein R¹ is H or methyl and R² is optionally substituted alkyl orcycloalkyl of 1 to 20 carbon atoms (more preferably 1 to 8 carbon atoms)examples of which are methyl acrylate, methyl methacrylate, ethylacrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate,2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isopropyl acrylate,isopropyl methacrylate, n-propyl acrylate, n-propyl methacrylate, andhydroxyalkyl (meth)acrylates such as hydroxyethyl acrylate, hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate,4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate and their modifiedanalogues like Tone M-100 (Tone is a trademark of Union CarbideCorporation).

Olefinically unsaturated monocarboxylic, sulphonic and/or dicarboxylicacids, such as acrylic acid, methacrylic acid, P-carboxy ethyl acrylate,fumaric acid, itaconic acid, sodio-4-sulpho-styrene (SSS),acrylamidopropane sulphonic acid (AMPS), (meth)acrylamide,methoxypolyethyleneoxide (meth)acrylate may also be used.

The vinyl monomer may optionally contain functional groups to contributeto the crosslinking of the vinyl polymer(s) in the coating. Examples ofsuch groups include maleic, epoxy, fumaric, acetoacetoxy, p-diketone,unsaturated fatty acid, acryloyl, methacryloyl, styrenic, (meth)allylgroups, mercapto groups, keto or aldehyde groups (such asmethylvinylketone, diacetoneacrylamide and (meth)acrolein).

Particularly preferred are vinyl polymer(s) made from a monomer systemcomprising at least 40 weight % of one or more monomers of the formulaCH₂═CR¹COOR² defined above. Such preferred vinyl polymer(s) are definedherein as acrylic polymer(s). More preferably, the monomer systemcontains at least 50 weight % of such monomers, and particularly atleast 60 weight %. The other monomers in such acrylic polymer(s) (ifused) may include one or more of the other vinyl monomers mentionedabove, and/or may include ones different to such other monomers.Particularly preferred monomers include butyl acrylate, butylmethacrylate, methyl methacrylate, ethyl hexyl methacrylate, esters of(meth)acrylic acid, vinyl and vinylidene chloride, butadiene,acrylonitrile, vinyl acetate and styrene.

If the dispersed polymer(s) is a dispersed vinyl polymer, the dispersedvinyl polymer optionally comprises at least 15 wt. %, more preferably atleast 40 wt. % and most preferably at least 60 wt. % of polymerisedvinyl acetate. If the dispersed vinyl polymer comprises at least 50 wt.% of polymerised vinylacetate then preferably the dispersed vinylpolymer also comprises 10 to 49 wt. % of either butylacrylate or abranched vinylester, for example Veova 10.

In a preferred embodiment the dispersed vinyl polymer comprises:

-   -   I. 15 to 60 wt. % of styrene and/or (x-methylstyrene;    -   II. 15 to 80 wt. % of one or more of methyl methacrylate, ethyl        methacrylate, cyclohexyl (meth)acrylate and n-butyl        methacrylate;    -   III. 0 to 5 wt. % of vinyl monomer containing carboxylic acid        groups;    -   IV. 0 to 10 wt. %, more preferably 0 to 5 wt. % of a vinyl        monomer containing non-ionic water-dispersing groups;    -   V. 5 to 40 wt. % of vinyl monomers other than as in I to IV, VI        and VII;    -   VI. 0 to 5 wt. % of vinyl monomers containing wet adhesion        promoters or crosslinker groups (excluding any within the scope        of III and VII); and    -   VII. 0 to 8 wt. %, more preferably 0 to 4 wt. %, and most        preferably 0.5 to 3 wt. % of a polyethylenically unsaturated        vinyl monomer,        wherein I)+II) add up to at least 50 wt. % and        I+II+III+IV+V+VI+VII add up to 100%.

The dispersed polymer(s) can be prepared by any known technique.Preparation techniques include either dispersing a pre-formed polymer orpolymer solution in water or if the dispersed polymer(s) is a vinylpolymer directly synthesising the vinyl polymer in water (for example byemulsion polymerisation, micro-suspension polymerisation or miniemulsion polymerisation). Methods for preparing aqueous dispersedpolymer(s) are reviewed in the Journal of Coating Technology, volume 66,number 839, pages 89–105 (1995) and these methods are included herein byreference. Preferably dispersed vinyl polymer(s) are prepared by theemulsion polymerisation of free radically polymerisable olefinicallyunsaturated monomers (Emulsion Polymerisation and Emulsion Polymers, P.Lovell, M. S. El-Aasser, John Wiley, 1997). Any published variant of theemulsion polymerisation process may be utilised to prepare the dispersedpolymer(s), including the use of seeded emulsion polymerisationtechniques to control particle size and particle size distribution,especially when working in the particle size range 300–700 nm when theseeded technique is useful for giving good particle size control. Otheruseful techniques are the so called sequential polymerisation techniqueand the power feed technique (chapter 23 in “Emulsion Polymers andEmulsion Polymerisation” D R Basset and A E Hamielec, ACS SymposiumSeries No 165,1981).

Preferably the dispersed polymer(s) is colloid stable and it is alsodesirable that colloid stability is maintained for as long as possibleinto the drying process since early loss of colloid stability can bringa premature end to open time. Since the final coating composition mayoften contain co-solvents and dissolved ionic species (e.g. from pigmentdissolution and from the presence of neutralising agents), it isdesirable that the colloid stability of the dispersed polymer(s) isadequate to withstand any destabilising influences of these components.Colloid stability may be achieved by the addition of conventionalnon-ionic surfactants, optionally with the addition of anionicsurfactants at any stage during the preparation of the aqueouscomposition of the invention. Strongly adsorbing surfactants capable ofproviding steric stability are preferred. Higher levels of colloidstability may be obtained by chemically binding or partially bindinghydrophilic stabilising groups such as polyethylene oxide groups to thesurface of dispersed polymer(s) particles. Suitable surfactants andstabilising groups are described in “Non Ionic Surfactants-PhysicalChemistry” (see for example M J Schick, M Dekker Inc 1987) and “PolymerColloids” (Buscall, Corner & Stageman, Elsevier Applied SciencePublishers 1985).

Chemical binding (grafting) of hydrophilic stabilising groups ontodispersed polymer(s) particles can be achieved by the use of acomonomer, polymerisation initiator and/or chain transfer agent bearingthe stabilising group, for example methoxy(polyethylene oxide)₃₀methacrylate may be introduced as a comonomer into an emulsionpolymerisation to give rise to stabilised dispersed polymer particleswith bound polyethylene oxide groups on the particle surface. Anothermethod of producing a strongly sterically stabilised dispersedpolymer(s) is to introduce cellulosic derivatives (e.g. hydroxy ethylcellulose) during an emulsion polymerisation (see for example D H Craig,Journal of Coatings Technology 61, no.779, 48, 1989). Hydrophilicstabilising groups may also be introduced into a preformed polymerbefore it is subsequently dispersed in water, as described in EP 0317258where polyethylene oxide groups are reacted into a polyester polymerwhich is subsequently dispersed in water and then chain extended.

The combination of crosslinkable polyester oligomer(s) (and othercrosslinkable or non-crosslinkable oligomers if used) and dispersedpolymer(s) is most conveniently prepared by physically blending thecorresponding aqueous dispersions. However other methods of preparingthe combination can sometimes be utilised. One such method is to preparethe crosslinkable polyester oligomer(s) in solution as previouslydiscussed, and to disperse this solution directly into a dispersedpolymer(s). Alternatively the solvent can be removed from thecrosslinkable polyester oligomer(s) solution, and the polyesteroligomer(s) is directly dispersed into a dispersed polymer(s). Anothermethod is to introduce the crosslinkable polyester oligomer(s) into anaqueous free radical polymerisation reaction which produces thedispersed polymer(s). Such an introduction of polyester oligomer(s) caneither be at the commencement of the aqueous free radical polymerisationor during an aqueous free radical polymerisation. (Also as mentionedpreviously, a dispersed polymer can sometimes be formed in-situ from thesynthesis of a polyester oligomer(s) as a very high molecular weightpolymer fraction resulting from the polyester synthesis).

The crosslinkable polyester oligomer(s) may also be diluted withreactive diluent (for example vinyl monomers) at any stage of itspreparation and then dispersed into a dispersed polymer(s), followed bypolymerisation of the reactive diluent in the presence of the polyesteroligomer(s) and the optional polymer dispersion(s). Optionally,depending on the nature of the reactive diluent, no furtherpolymerisation of the reactive diluent prior to use in a coating may berequired.

Alternatively the crosslinkable polyester oligomer(s) and dispersedpolymer(s) may be combined by preparing a redispersible dry powder formof the dispersed polymer(s), and then dispersing the redispersible drypowder directly into an aqueous dispersion of the crosslinkablepolyester oligomer(s). Methods for preparing redispersible dry powdersfrom polymer emulsions are described for example in U.S. Pat.No.5,962,554, DE 3323804 and EP 0398576.

In an embodiment of the invention the crosslinkable polyesteroligomer(s) and the optional dispersed polymer(s) are compatible in thedrying aqueous composition. Preferably the crosslinkable polyesteroligomer(s) and the dispersed polymer(s) give clear films upon filmformation after coating of the aqueous composition onto a substrate.

Preferably the ratios by weight of solid material of crosslinkablepolyester oligomer(s) (and other crosslinkable or non-crosslinkableoligomers if used) to the dispersed polymer(s) in the range of from100:0 to 10:90, more preferably in the range of from 90:10 to 20:80,still more preferably in the range of from 80:20 to 25:75 and especiallyin the range of 60:40 to 30:70.

The aqueous coating composition of the invention is particularly usefulas or for providing the principle component of coating formulations(i.e. composition intended for application to a substrate without anyfurther treatment or additions thereto) such as protective or decorativecoating compositions (for example paint, lacquer or varnish) wherein aninitially prepared composition may be optionally further diluted withwater and/or organic solvents and/or combined with further ingredients,or may be in more concentrated form by optional evaporation of waterand/or organic components of the liquid medium of an initially preparedcomposition. The invention composition can contain co-solvent or amixture of co-solvents. Preferably the invention composition contains±18% by weight of cosolvent(s), more preferably ±10%, still morepreferably ±5%, especially ±3% and most especially 0% by weight based onthe invention composition. Preferably the evaporation rate of theco-solvent is ≦0.6, more preferably ≦0.15 most preferably ≦0.08, andespecially ≦0.035. Values for evaporation rates were published by TexacoChemical Company in a bulletin Solvent Data: Solvent Properties 1990.These values are relative to the evaporation rate of n-butylacetate forwhich the evaporation rate is defined as 1.00. Determinaton of theevaporation rate of solvents that are not listed in this bulletin is asdescribed in ASTM D3539.

In a special embodiment, the amount of co-solvent used in the inventioncomposition is preferably linked to the Mw in the range 1,000 to 120,000Daltons, the amount of co-solvent is preferably 0 to 15 wt. % based onthe weight of the composition, more preferably 0 to 10 wt. %. Foroligomers with Mw in the range >50,000 to 100,000 Daltons, thecorresponding figures for the preferred amount of co-solvent are 0 to 25wt. %, more preferably 5 to 20 wt. %.

Furthermore, there is also a preferred relationship between the amountof co-solvent used and the amount of binder polymer solids, and theamount of co-solvent is preferably ≦50 wt. % based on the weight ofbinder polymer solids in the composition, more preferably ≦35 wt. %,still more preferably ≦20 wt. %, most preferably ≦10 wt. % andespecially 0 wt. %.

An advantage of the current invention is that co-solvent can, if as isoften required for environmental and safety reasons, be present at avery low concentrations because of the plasticising nature of thecrosslinkable polyester oligomer(s). Preferably the solvent to waterratio is below 1.0, more preferably below 0.5, most preferably below 0.3and especially below 0.15. The co-solvent(s) can all be added at thefinal formulation step. Alternatively some or all of the co-solvent inthe final formulation can be the co-solvent utilised in the preparationof the crosslinkable polyester oligomer. An important consideration whenchoosing a co-solvent is whether or not the co-solvent is compatiblewith the crosslinkable polyester oligomer(s) and/or the dispersedpolymer(s) and the effect of any co-solvent partitioning (and thepartitioning of the co-solvent in the (aqueous) polyester oligomer phaseversus the dispersed polymer particles is preferably >1/1, morepreferably >2/1 and most preferably >3/1). If the co-solvent is morecompatible with the polymer it will swell the polymer, thus increasingthe overall viscosity. Preferably any co-solvent present in the aqueouscomposition of the invention is more compatible with the polyesteroligomer(s) then with the dispersed polymer(s), so that the dispersedpolymer(s) undergoes little if any swelling by the co-solvent. Theco-solvent selection is often determined by experimentation and/or bythe use of a solubility parameter concept i.e. maximising the differencein the solubility parameter of the dispersed polymer(s) and solventleads to a minimisation of the co-solvent uptake by the dispersedpolymer(s). Solubility parameters of a range of solvents and a groupcontribution method for assessing the solubility parameters of polymersare given by E A Grulke in the “Polymer Handbook” (John Wiley pages519–559, 1989) and by D W Van Krevelen and P J Hoftyzer in “Propertiesof Polymers. Correlations With Chemical Structure” (Elsevier, N.Y., 1972chapters 6 and 8). Co-solvent uptake of the dispersed polymer(s) may bedecreased by increasing the Tg so that the dispersed polymer(s) is inthe glassy region at ambient temperature, or by pre-crosslinking thedispersed polymer(s) as described above. Other ways of introducingpre-cross linking into dispersed polymer(s) are known in the art, forexample U.S. Pat. No. 5,169,895 describes the preparation ofpre-crosslinked polyester aqueous dispersions by the use oftri-functional isocyanates in the synthesis.

A known problem with many autoxidisable coating compositions is that theresultant coatings have a tendency to yellow, in particular where theautoxidisable groups are derived from polyunsaturated fatty acids, suchas for example tung oil, linolenic acid, eleostearic acid, arachidonicacid, clupanadonic acid, and fatty acids obtainable from dehydratedcastor oil. This may be unacceptable depending on the desired colour ofthe resultant coating. Preferably the aqueous composition has a startingyellowness value of less than 10, more preferably less than 7 and mostpreferably less than 4, when measured using the test method describedherein. Preferably the aqueous composition has an increase in yellowingin darkness of less than 7, more preferably less than 5, most preferablyless than 3 and preferably the aqueous composition has an increase inyellowing in daylight less than 12, more preferably less than 8 and mostpreferably less than 4 as measured by the test method described herein.Furthermore, the absolute yellowness (i.e. yellowness at start plusyellowness due to ageing) of the aqueous composition is preferably lessthan 12, more preferably less than 10, still more preferably less than8, and most preferably less than 6.

In a further embodiment of the present invention there is provides anaqueous coating composition as defined herein comprising:

-   -   i) 3 to 26% of a crosslinkable oligomer(s) by weight of the        composition of which at least 52 wt % is said crosslinkable        polyester oligomer(s);

ii) 0 to 6.5% of a non-crosslinkable oligomer(s) by weight of thecomposition;

iii) 10 to 56% of dispersed polymer(s) by weight of the composition;

iv) 0 to 15% of co-solvent by weight of the composition;

v) 5 to 65% of water by weight of the composition;

where i)+ii)+iii)+iv)+v)=100%.

In another embodiment of the present invention there is provided anaqueous coating composition as defined herein comprising:

i) 15 to 40% of a crosslinkable oligomer(s) by weight of crosslinkableoligomer(s) and non-crosslinkable oligomer(s) and dispersed polymer(s)of which at least 52 wt % is said crosslinkable polyester oligomer(s);

ii) 0 to 10% of a non-crosslinkable oligomer(s) by weight ofcrosslinkable oligomer(s) and non-crosslinkable oligomer(s) anddispersed polymer(s);

iii) 50 to 85% of dispersed polymer(s) by weight of crosslinkableoligomer(s) and non-crosslinkable oligomer(s) and dispersed polymer(s);

where i)+ii)+iii)=100%.

The aqueous coating composition of the invention may be applied to avariety of substrates including wood, board, metals, stone, concrete,glass, cloth, leather, paper, plastics, foam and the like, by anyconventional method including brushing, dipping, flow coating, spraying,and the like. They are, however, particularly useful for providingcoatings on wood and board substrates. The aqueous carrier medium isremoved by natural drying or accelerated drying (by applying heat) toform a coating.

Accordingly in a further embodiment of the invention there is provided acoating obtainable from an aqueous coating composition of the presentinvention. The aqueous coating composition of the invention may containother conventional ingredients including pigments, dyes, emulsifiers,surfactants, plasticisers, thickeners, heat stabilisers, levellingagents, anti-cratering agents, fillers, sedimentation inhibitors, UVabsorbers, antioxidants, dispersants, pigments, defoamers, co-solvents,wetting agents and the like introduced at any stage of the productionprocess or subsequently. It is possible to include an amount of antimonyoxide in the dispersions to enhance the fire retardant properties.Optionally external crosslinking agent(s) may be added to the aqueouscomposition of the invention to aid crosslinking during or after drying.Examples of reactive functional groups which may be utilised forexternal linking agent(s) include but are not limited to hydroxylfunctional groups reacting with isocyanate (optionally blocked),melamine, or glycouril functional groups; keto, aldehyde and/oracetoacetoxy carbonyl functional groups reacting with amine or hydrazinefunctional groups; carboxyl functional. groups reacting with aziridine,epoxy or carbodiimide functional groups; silane functional groupsreacting with silane functional groups; epoxy functional groups reactingwith amine or mercaptane groups as well as carboxyl functional groupsundergoing metal ion (such as zinc) crosslinking.

In particular, the aqueous coating compositions of the invention (ifautoxidisable) and formulations containing them advantageously include adrier salt(s). Drier salts are well known to the art for furtherimproving curing in unsaturated film-forming substances. Generallyspeaking, drier salts are metallic soaps, that is salts of metals andlong chain carboxylic acids. It is thought that the metallic ions effectthe curing action in the film coating and the fatty acid componentsconfer compatibility in the coating medium. Examples of drier metals arecobalt, manganese, zirconium, lead, neodymium, lanthanum and calcium.The level of drier salt(s) in the composition is typically that toprovide an amount of metal(s) within the range of from 0.01 to 0.5% byweight based on the weight of autoxidisable polyester oligomer(s) and orautoxidisable dispersed polymer(s).

Drier salts are conventionally supplied as solutions in white spirit foruse in solvent-borne alkyd systems. They may, however, be used quitesatisfactorily in aqueous coating compositions since they can normallybe dispersed in such systems fairly easily. The drier salt(s) may beincorporated into the aqueous coating composition at any convenientstage. For example the drier salt(s) may be added prior to dispersioninto water. Drier accelerators may be added to the drier salts. Suitabledrier accelerators include 2,2′-bipyridyl and 1,10-phenanthroline.

If desired the aqueous dispersion of the invention can be used incombination with other polymer dispersions or solutions which are notaccording to the invention.

The present invention is now illustrated by reference to the followingexamples. Unless otherwise specified, all parts, percentages and ratiosare on a weight basis. The prefix C before an example denotes that it iscomparative. The term “working” means that the example is according tothe invention. The term “non-working” means that it is not according tothe invention (i.e. comparative).

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 illustrate the drying profile of a composition according tothe present invention [Example 6], where the equilibrium viscosity ismeasured as the solids content increases.

FIG. 1 shows the drying profile measured using a shear rate of 0.0997s⁻¹.

FIG. 2 shows the drying profile measured using a shear rate of 0.990s⁻¹.

FIG. 3 shows the drying profile measured using a shear rate of 9.97 s⁻¹.

FIG. 4 shows the drying profile measured using a shear rate of 78.6 s⁻¹.

TEST METHODS

To test the open time and wet edge time aqueous compositions prepared asdescribed in the examples below were applied using a wire rod to a testchart (18×24 cm, form 8B—display, available from Leneta Company) at awet film thickness of 120 μm. Open time and wet edge time tests wereperformed at fairly regular time intervals according to the approximateexpected final time in each case (being determined roughly from a trialrun), the intervals between measurements decreasing towards the end ofthe run. The measurements were carried out at relative humidity levelsof 50+/−5%, temperatures of 23+/−2° C. and an air flow ≦0.1 m/s.

Open Time:

The open time was determined by brushing a virgin 75 cm² area of thecoated chart with a brush (Monoblock no 12, pure bristles/polyester5408-12) carrying at regular intervals (as mentioned above) some more ofthe composition with a brush pressure of 100–150 g during 30 seconds. Inthis time the brush was moved in one set comprising 5 times in thedirection of the width of the substrate and 5 times in the direction oflength of the substrate before the coating was visually assessed. Oncethe composition carried on the brush no longer formed a homogeneouslayer with the coating on the substrate the open time was considered tobe over.

Wet Edge Time:

The wet edge time was determined by brushing at regular intervals (asmentioned above) a virgin 25 cm² edge area of the coated chart with abrush (Monoblock no 12, pure bristles/polyester 5408-12) carrying somemore of the composition with a brush pressure of 100–150 g during 30seconds. In this time the brush was moved in one set comprising 5 timesin the direction of the width of the substrate and 5 times in thedirection of length of the substrate before the coating was visuallyassessed. Once the composition carried on the brush no longer formed ahomogeneous layer with the coating on the substrate and/or a visible lapline could be seen the wet edge time was considered to be over.

Drying Time:

To test the dust-free, tack-free and thumb-hard drying stages of theaqueous compositions prepared in the Examples as described below, thecomposition was applied to a glass plate at a wet film thickness of 80μm. Drying time tests were performed at regular time intervals atrelative humidity levels of 50+/−5%, temperatures of 23+/−2° C. and anair flow ≦0.1 m/s.

Dust-free Time:

The dust-free time was determined by dropping a piece of cotton wool(about 1 cm³ i.e. 0.1 g) onto the drying film from a distance of 25 cm.If the piece of cotton wool could be immediately blown from thesubstrate by a person without leaving any wool or marks in or on thefilm, the film was considered to be dust-free.

Tack-free Time:

The tack-free time was determined by placing a piece of cotton wool(about 1 cm³, 0.1 g) on the drying film and placing a metal plate (witha diameter of 2 cm) and then a weight of 1 kg onto the piece of cottonwool (for 10 seconds). If the piece of cotton wool could be removed fromthe substrate by hand without leaving any wool or marks in or on thefilm, the film was considered to be tack-free.

Thumb-hard Time:

The thumb-hard time was determined by placing the coated glass plate ona balance and a thumb was pressed on the substrate with a pressure of 7kg. The thumb was then rotated 90° under this pressure. If the film wasnot damaged the coating was dried down to the substrate level andconsidered to be thumb-hard.

Viscosity:

All viscosity measurements were performed on a Bohlin Rheometer VOR or aTA Instruments AR1000N Rheometer, using the cup & spindle (C14), cone &plate (CP 5/30) and/or plate & plate (PP15) geometry, depending on theapproximate viscosity of the sample to be measured.

Solution Viscosity

For the solution viscosity measurements (both at 50±2° C. and at 23±2°C.), the cone & plate (CP 5/30) geometry was used and the measurementswere performed at a shear rate of 92.5 s⁻¹. If the oligomer solutionswere too low in viscosity to remain in between the cone and the plate,the Cup & Spindle C14 geometry was used and the viscosity measurementswere performed at a shear rate of 91.9 s⁻¹. For both geometries, the gapbetween the Cone and the Plate (or between the Cup and the Spindle) wasset to 0.1 mm, prior to each measurement. The solution viscosities ofthe oligomers were measured using the solvent systems and the conditionsas defined herein in the statements of invention:

-   1. The 80% solids solution: The oligomer was diluted (if necessary)    with the appropriate solvent to an 80% solids solution (in NMP, BG    or a mixture of NMP and BG at any ratio) which was homogenised by    stirring the solution for 15 minutes at 50±2° C.-   2. The 70% solids solution: The oligomer was diluted with the    appropriate solvent (or mixture of solvents) to result in a 70%    solids solution (either in NMP/water/DMEA or in BG/water/DMEA, or in    (a mixture of NMP and BG at any ratio)/water/DMEA; in both solvent    mixtures the solvents should be present in a weight ratio of 20/7/3,    respectively) which was homogenised by stirring the solution for 15    minutes at 50° C. The resulting solution was subsequently cooled    prior to the viscosity measurement at 23±2° C.-   3. A sample of oligomer solution was placed in the appropriate    measurement geometry (Cone & Plate CP 5/30 or Cup & Spindle C14    geometry). The solution viscosity of the oligomer was measured at a    temperature of 50±2° C. for the 80% solids oligomer solution, and at    ambient temperature for the 70% solids oligomer solution. A    heating/cooling unit in the measurement geometry was used to control    the temperatures.    Equilibrium Viscosity:

The equilibrium viscosity measurements were performed with the plate &plate geometry, with a 15 mm (P15) top-plate and a 30 mm (P30)bottom-plate. The gap between the two plates was set to 1.0 mm. Allcompositions were used at the solids level at which they were preparedand not diluted to lower solids levels.

-   Step 1: Three test charts were provided with coatings of identical    film thickness. The coatings were applied with a 120 μm wire rod and    the actual film thickness (and its uniformity) was checked with a    wet film gauge, 20–370 μm, of Braive Instruments. The charts were    dried under identical conditions in an environment where the airflow    was <0.1 m/s.-   Step 2: One test chart was used to determine the solids increase in    time. The weight of the film was monitored in time, starting right    after application of the film. After calculating the solids content    at every measurement, a solids-time curve could be constructed and a    trend line was calculated for the solids of the film as a function    of the drying time.-   Step 3: The other two test charts were used to determine the    equilibrium viscosity in time: approximately every 5 minutes a    sample was scraped from one test chart (in random order) and the    viscosity of this sample was measured at 23° C. at representative    shear rates of 0.0997 s⁻¹, 0.990 s³¹ ¹, 9.97 s⁻¹ and 78.6 s⁻¹. The    measurements were continued for 90 minutes, unless reproducible    sampling from the test charts could not be performed properly within    that period of time (due to for example drying of the film to reach    the dust free time).-   Step 4: The final drying curve of the coatings as shown in FIGS. 1    to 4 (in which the equilibrium viscosity is represented as a    function of the solids of the drying film) could be constructed from    the solids-time curve (Step 2) and the equilibrium viscosity data    (Step 3). If the equilibrium viscosity at a shear rate of 9.97 s³¹    ¹, is lower than the equilibrium viscosity at a shear rate of 0.99    s³¹ ¹, which is turn is lower than the equilibrium viscosity at a    shear rate of 0.0997 s⁻¹, the composition may be regarded as shear    thinning. If this was the case the equilibrium viscosity at 78.6 s⁻¹    was not always measured as it would inherently always be lower than    the equilibrium viscosity at a shear rate of 9.97 s⁻¹.    Measurement of Yellowing:

The yellowness of a fresh coating and the increased yellowing of acoating exposed to daylight or darkness for a specified time period wasdetermined using a Tristimulus Colorimeter consisting of a data-station,a micro-colour meter, a calibration plate with a defined x, y and zvalue and a printer. The equipment was calibrated to the defined valuesof the calibration plate and then colour co-ordinates L, a and b, weremeasured. The colour co-ordinates define the brightness and colour on acolour scale, where ‘a’ is a measure of redness (+a) or greenness (−a)and ‘b’ is a measure of yellowness (+b) or blueness (−b), (the moreyellow the coating, the higher the ‘b’ value). The co-ordinates ‘a’ and‘b’ approach zero for neutral colours (white, grays and blacks). Thehigher the values for ‘a’ and ‘b’ are, the more saturated a colour is.The lightness ‘L’ is measured on a scale from 0 (white) to 100 (black).

The yellowing in daylight is defined as in the increase of theyellowness (Δb-day) of the coating during storage at 23±2° C. and indaylight for 28 days. The yellowing in the dark is defined as theincrease in the yellowness (Δb-dark) of the coating during storage at23±2° C., in the dark for 14 days.

Molecular Weight Determination:

Gel permeation chromatography (GCP) analyses for the determination ofpolymer molecular weights were performed on an Alliance Water 2690 GPCwith two consecutive PL-gel columns (type Mixed-C, I/d=300/7. mm) usingtetrahydrofuran (THF) as the eluent at 1 cm³/min and using an AllianceWaters 2410 refractive index detector. A set of polystyrene standards(analysed according to DIN 55672) was used to calibrate the GPC.

Samples corresponding to about 16 mg of solid material were dissolved in8 cm³ of THF, and the mixtures were stirred until the samples haddissolved. The samples were left undisturbed for at lest 24 hours forcomplete “uncoiling” and subsequently were filted (Gelman Acrodisc 13 or25 mm ø CR PTFE; 0.45 μm) and placed on the auto-sampling unit of theGPC.

All species with a molecular weight less than 1000 Daltons were ignoredwhen calculating the Mw and PDi for the oligomers. When Daltons are usedin this application to give molecular weight data, it should beunderstood that this is not a true molecular weight, but a molecularweight measured against polystyrene standards as described above.

Water Solubility Determination by a Centrifuge Test:

A sample of for example a crosslinkable polyester oligomer was dispersedin water and diluted with water/ammonia to 10% solids and the pHadjusted to the desired pH, within a range of from 2 to 10, and thedispersion was then centrifuged over 5 hours at 21000 rpm at 23±2° C. ona Sigma 3K30 centrifuge (21,000 rpm corresponds to a centrifugal forceof 40,000 g. The pH chosen should be the pH where the crosslinkablevinyl oligomer is expected to be most soluble, for example often a pH ofabout 9 is suitable for anionic stabilised dispersions and a pH of about2 is often suitable for cationic stabilised dispersions. Aftercentrifugation a sample of the supernatant liquid was taken andevaporated for 1 hour at 105° C. to determine the solids content of thesupernatant liquid. The water solubility percentage was calculated bydividing the amount of solids (in gram) of the supernatant by the totalamount of solids put in the centrifuge tube and multiplying this by 100.

Water Resistance

The aqueous compositions prepared in the examples below were cast downon Leneta test charts Form 2C with a film thickness of 120 μm. The filmswere dried at room temperature for 4 hours and at 50° C. for 16 hours.After they were cooled down to room temperature the films were testedfor water resistance. A few drops of water were placed on the films andcovered with a watch glass. The water was removed after 16 hours at roomtemperature and the damage to the coating was assessed immediately andafter four hours recovery. 0 Means that the coat is dissolved, 5 meansthat the coating is not affected at all.

Materials & Abbreviations used: DEA = N,N-diethylethanolamine CarduraE10 = Neodecanoic acid-2,3-epoxypropyl ester available from ShellMPEG750 = methoxypolyethylene glycol (Mn apprxoximately 750) DMPA =dimethylolpropionic acid NMP = N-methyl pyrrolidone TDI = toluenediisocyanate Dowanol DPM = dipropylene glycol monomethyl ether DAPRO5005= drier salt available from Profiltra 1,4-CHDM =1,4-cyclohexanedimethanol Voranol P-400 = polypropyleneglycol availablefrom DOW Chemical A1310 = NCO functional silane component available fromCK Witco Corporation DMBA = dibutylbutanoic acid TMPME =trimethylolpropanemonoallyl ether TMPDE = trimethylpropanediallyletherIPDI = isophorone diisocyanate TEA = triethylamine Combi LS = drier saltavailable from Servo Delden Boltorn H20 = Dendritic polymer availablefrom Perstorp Nouracid LE80 = linseed oil fatty acid available from AKZONobel Fastcat 2005 = tin(II)chloride available from Elf-Atochem MEK =methyl ethyl ketone Atlas 4809 = Alkyl phenol alkoxylate available fromATLAS Chemie Atpol E5720/20 = Fatty alcohol ethoxylate available fromUniqema AP = ammonium persulphate Aerosol OT-75 = Sodiumdioctylsulphosuccinate available from Cytec MMA = methylmethacrylaten-BA = n-butylacrylate AA = acrylic acid SLS = Sodium Lauryl SulphateAkyposal NAF = Sodium dodecylbenzenesulphonate available from KAOChemicals Natrosol 250LR = Hydroxy ethyl cellulose available fromHercules Akyporox OP-250V = Octyl phenol ethoxylate available from KAOChemicals Surfactant = Phosphate ester of nonyl phenol ethoxylateavailable from KAO Chemicals VeoVa 10 = Vinyl ester of versatic acidavailable from Shell Desmodur W = dicyclohexyl methane diisocyanateavailable from Bayer Priplast 3192 = Dimeric acid polyester polyolavailable from Uniqema BMA = n-butyl methacrylate t-BHPO = t-butylhydroperoxide Fe^(III).EDTA = ferric ethylene diamine tetracetic acidIAA = isoascorbic acid solution STY = Styrene 2-EHA =2-Ethylhexylacrylate Dynasilan MEMO =3-Methacryloxypropyltrimethoxysilane available from Degussa HEMA =Hydroxyethylmethacrylate TEGDMA = Triethyleneglycoldimethacrylate OMKT =n-octyl mercaptane TAPEH = tert-amylperoxy-2-ethyl hexanoate SilquestA.174NT = 3-methacryloxypropyl trimethoxysilane available from WitcoWater = demineralised water PW602 = Transparent red iron-oxide pigmentdispersion available from Johnson Matthey AMP-95 =2-amino-2-methyl-1-propanol (available from Integrated Chemicals bv, 95%in water) Dehydran 1293 = Defoamer additive available from Cognis; 10%in butyl glycol Surfynol 104 E = wetting agent available from AirProducts; 50% in ethylene glycol NeoCryl BT-24 = Acrylic emulsionpolymer available from NeoResins, Avecia bv SAN = succinic anhydride ADH= Adipic acid dihydrazidePreparation of a Poly-alkoxylated Adduct MPEG750/SAN:

A 2-L 3-necked round bottom flask, equipped with stirrer, was loadedwith methoxypolyethylene glycol (Mn ca. 750; 1323.53 g) and succinicanhydride (176.47 g) in a nitrogen atmosphere. The reaction mixture washeated to 120° C, and was stirred at this temperature until all theanhydride had reacted, as judged from the Infra Red spectrum of thereaction mixture (the anhydride groups typically show two absorptions at1785 cm⁻¹ and 1865 cm⁻¹, which disappeared and were replaced by a newester carbonyl absorption at 1740 cm⁻¹). The clear liquid product wasthen cooled to 50° C. and collected. The product solidified when leftundisturbed at ambient temperature.

Crosslinkable Polyester Oligomer E1:

Phase 1: A 2 litre, five-necked reactor flask fitted with a stirrer, athermometer and a condenser fitted with a Dean-Stark condensate trap,was loaded with adipic acid (156.49 g), Prifac 8961 (sunflower oil fattyacid, Trademark from Uniqema; 391.22 g), trimethylol propane (TMP; 78.24g) and pentaerythritol (PE; 130.41 g) in a nitrogen atmosphere. Theresulting slurry was heated to 210° C. under vigorous stirring and thereaction water was distilled off. After two hours of reaction time, aportion of Fastcat 2005 (stannous(II)chloride, Trademark fromElf-Atochem; 0.26 g) was added to the reaction mixture. After 6 hoursreaction time the acid value had dropped to 6.5 mg KOH/g and the viscousmixture was cooled to 120° C. In the second phase succinic anhydride(78.24 g) was added to the reaction mixture in one portion. The contentsof the reactor were stirred at 120° C. until all the anhydride hadreacted, as judged from the Infra Red spectrum of the reaction mixture(the anhydride groups typically show two absorptions at 1785 cm⁻¹ and1865 cm⁻¹, which disappeared and were replaced by a new ester carbonylabsorption at 1740 cm⁻¹). The resultant acid-functional polyesteroligomer E1 was cooled to room temperature and collected. The oligomerhad an acid value of 54 mg KOH/g.

The polyester oligomer had a viscosity of 523 mPa.s, when measured at ashear rate of 91.9 5 s⁻¹, at 50° C. and at a solids content of 80% byweight in BG, and a viscosity of 1,130 mPa.s, when measured at a shearrate of 91.9 s⁻¹, at 23° C. and at a solids content of 70% by weight ina solvent mixture of BG/H₂O/DMEA=20/7/3.

The crosslinkable polyester oligomers E2 to E8 were prepared accordingto similar procedures using the components shown in Table 1 below, withthe following changes:

Crosslinkable Polyester Oligomer E2:

3-Isocyanato-propyl triethoxy silane (Silquest A-1310)post-modification, for the preparation of oligomer E2, was performed bymixing the OH-functional hyper-branched polyester and IPTS at roomtemperature, followed by addition of a catalytic amount of dibutyltindilaurate and subsequent heating of the reaction mixture to 50° C. Themixture was stirred at this temperature until all the isocyanate hadreacted, as judged from the Infra Red spectrum of the reaction mixture(the NCO groups typically show an absorption at 2275 cm⁻¹). NMP was usedas co-solvent in this reaction.

Crosslinkable Polyester Oligomer E3:

The polyester oligomer E3, with a combination of fatty acid and allylfunctionality, was prepared by the reaction of an OH-functional fattyacid polyester oligomer (the product of phase 1 and 2), with SAN (phase3), followed by the reaction of the resulting carboxylic acid groupbearing polyester with allyl glycidyl ether (AGE) at 110° C. (phase 4).

Crosslinkable Polyester Amide Oligomer E8:

The polyester amide oligomer E8 was prepared from a fatty amide. Thefatty amide was prepared by the reaction of N,N-diethanolamine withsunflower oil, catalysed by NaOMe, by stirring the reaction mixture for4 hours at 110° C. in a nitrogen atmosphere. The esterification reactionto form oligomer 8 was conducted at 180° C. until an acid value of 20 mgKOH/g was obtained. This acid value corresponds to the theoretical acidvalue when the acid group of DMPA is left unreacted. The OH value was264 mg/KOH.

Water Solubility

Crosslinking polyester oligomers E2, E4 and E7 were respectively 100%,7.9% and 32.5% water soluble as measured by the centrifuge test.

TABLE 1 Components E2^(b) E3^(c) E4^(d) E5 E6 E7 E8 Isophthalic acid (g)— — — 93.86 — — — Adipic acid (g) 242.32 101.25 234.89 — — 300.00 295.61CHDA (g) — — — — 158.30 — — DMPA (g) — — — — — — 68.26 Levulinic acid(g) 170.20 — — — — 150.00 — Fatty acid — — Prifac Dedico Prifac Prifac —8961 5981 8961 8961 Fatty acid (g) — — 392.70 40.91 1273.50 500.00 —Fatty amide (g) — — — — — — 918.50 SSIPA (g) — 38.56 — — — 76.50 — NPG(g) 52.40 69.43 44.00 17.45 — 128.25 — Trimethylolpropane (g) 230.9160.26 328.84 54.88 134.10 280.00 — Pentaerythritol (g) — — — 24.55134.10 — — MPEG 750 (g) — — — — — — 72.00 MPEG 750/SAN (g) 55.12 120.22— 35.55 — — — CHDM (g) — — — — — — 31.62 SnCl₂.H₂O (catalyst) (g) 0.300.50 0.50 0.07 1.00 0.50 0.50 Acid value (mg KOH/g) 5.80 4.20 5.20 1.600.86 8.40 19.60 CoatOSil CS1770 (g) — 143.10 — — — — — SAN (g) 35.50 —60.00 43.40 — — — DMAP (g) 0.70 — 0.10 0.20 — — — DBTDL (g) — 0.10 — — —— — Allyl glycidyl ether (g) — — 57.00 — — — — DMBA (g) — — 4.00 — — — —BG (g) — — — — — — — NMP (g) — 125.03 9.90 71.82 — — — Final Acid value(mg KOH/g) 33.94 3.01 5.47 91.54 0.86 8.40 19.60 Solution viscosity*2950 10100 131 135000 41 336 198 Solution viscosity** 3920 5540 34988300 356 551 457 Mw 39456 32370 3621 24542 59300 3599 7422 PDi 21.615.7 2.0 12.4 6.7 2.7 3.5 ^(b)Phase 1: AA, MPEG750/SAN, TMP, NPG; phase2: levulinic acid; phase 3: SAN, DMAP ^(c)Phase 1: TMP, NPG, SSIPA;phase 2: AA, MPEG750/SAN; phase 3: CoatOSil CS1770, DBTDL, NMP ^(d)Phase1: AA, TMP, NPG; phase 2: Prifac 8961; phase 3: SAN, DMAP, NMP; phase 4:AGE, DMBA *50° C., 80% solids in NMP at 91.9 s-1 (mPa · s) **23° C., 70%solids in NMP/H2O/DMEA at 91.9 s-1 (mPa · s)Preparation of Dispersion dE1 from Crosslinkable Polyester Oligomer E1:

A 500 cm³ three-necked reactor flask fitted with a stirrer and athermometer was charged with the polyester oligomer E1 solution (200.0g, 80% solids) prepared above and the content was heated to 65° C. undera nitrogen atmosphere. At this temperature, a drier salt (DAPRO5005,trademark from Profiltra, 2.4 g), dipropylene glycol methyl ether (20.54g), ATLAS G4809 (trademark from Uniqema, 70% aqueous solution, 8.0 g),N,N-dimethyl ethanolamine (DMEA, 17.13 g) and water (53.86 g) weresubsequently added to the stirred polyester oligomer solution while thetemperature was kept at 65° C. The resulting mixture (275.0 g) wasslowly added over a period of 30 minutes to hot water (333.93 g, 50° C.)in a 1-L reactor under a nitrogen atmosphere while the temperature ofthe stirred aqueous phase was kept at 45 to 50° C. The resultingdispersion was stirred for an additional 30 minutes at 45 to 50° C. andsubsequently cooled to room temperature, filtered and collected. Theresultant translucent polyester dispersion dE1 had a solids content of26.3%.

The crosslinkable polyester oligomer dispersions dE2 to dE8 wereprepared according to similar procedures using the components listed inTable 2 below. Polyester oligomers that were dispersed with the use of amini-emulsion prepared from the Atlas G5000, dodecanol and water (dE4,dE5 and dE6) were dispersed under high shear (Dispermat, 7000 rpm). DE8was first prepared as a predispersion. DE2 included as additives NH₃(25% aq, 4.55 g) and ADH (2.7 g) and dE7 included ADH (1.11 g) as anadditive.

TABLE 2 Components dE2 dE3 dE4 dE5 dE6 dE7 dE8 Oligomer (g) 50.00 51.0050.00 42.90 50.00 50.00 150.00 Dodecanol (g) — — 2.00 2.00 2.00 1.32 —NMP or DPM* (g) — — — 8.58 2.50* — 22.5/15.0* DAPRO 5005 (g) or — — 1.001.00 1.00 1.00** 2.25 Borchersdry VP0133** (g) ATLAS G5000 — — 2.00 2.002.00 1.32 — Neutralising agent type DMEA NH₃ DMEA DMEA DMEA NH₃ DMEANeutralising agent (g) 2.80 3.16 0.40 5.20 0.06 0.55 4.67 Water (g)106.20 81.80 72.10 26.05 72.40 101.87 36.78 Dispersion solids (%) 31.730.1 40.9 40.1 40.1 33.0 65.0 Dispersion pH 8.2 7.9 7.1 7.7 7.0 7.6 7.7NH₃ was used as 25% aqPreparation of a Crosslinkable Urethane Oligomer U1, and Its DispersionDU1:

The first step of this preparation provides an isocyanate-reactivematerial bearing crosslinker groups for use in the synthesis of theself-crosslinkable polyurethane oligomer, the isocyanate-reactive groupsbeing hydroxyl and the crosslinker groups being fatty acid groups. A 1-L3-necked round bottom flask, equipped with a stirrer and a thermometer,was loaded with N,N-diethanolamine (DEA) (100.00 g), NaOMe (0.52 g) andsunflower oil (505.10 g) in a nitrogen atmosphere. The hazy reactionmixture was stirred at 110–120° C. until a clear mixture was obtained.Stirring at the given temperature was continued until a DEA-conversionof at least 90% was achieved, as determined by titration of residualamine functionality in the product with 1 N aqueous HCl. A conversion of94% was achieved. The product was then cooled to room temperature andstored under nitrogen.

In the second step, a 1-L 3-necked round bottom flask, equipped with astirrer and a thermometer, was loaded with dimethylolpropanoic acid(DMPA; 19.36 g), N-methyl pyrrolidone (NMP; 92.50 g),methoxypolyethylene glycol (MPEG750; 18.87 g), cyclohexane dimethanol(CHDM; 8.97 g), the alkyd polyol mixture described above (260.43 g) andtoluene diisocyanate (TDI; 99.89 g). The reactor was purged withnitrogen and the reaction mixture was slowly heated to 50° C. andstirred at this temperature for 1 hour in a nitrogen atmosphere. Themixture was then heated to 80° C. and kept at this temperature for 1hour. The resultant NCO-free alkyd urethane oligomer U1 was then cooledto 70° C. and diluted with dipropylene glycol monomethyl ether (51.38g), N,N-dimethylethanolamine (DMEA; 10.27 g), DAPRO 5005 (5.84 g) andwater (155.43 g). The mixture was homogenised at 55 to 60° C. andsubsequently fed into water (907.1 g; 50° C.) in a separate reactor in anitrogen atmosphere. The product dispersion was cooled to ambienttemperature, filtered and stored in a nitrogen atmosphere. Thedispersion DU1 has a solids content of 24.2% and a pH of 7.1.

-   The viscosity of an 80% solids solution in NMP (50° C., shear rate    91.1 s⁻¹) is 6.61 Pa.s.-   The viscosity of a 70% solids solution in NMP/H₂O/DMEA (20/7/3) (23°    C., shear rate 91.9 s⁻¹) is 10.91 Pa.s.-   GPC analysis of U1: Mw=4,917; Mn=2,535; PDi=1.94-   Acid value of U1=19.1 mgKOH/g    Preparation of a Non-Crosslinkable Urethane Oliqomer U2, and Its    Dispersion DU2:

In a nitrogen atmosphere, a 1-L 3-necked round bottom flask, equippedwith a stirrer and a thermometer, was loaded with dimethylolpropanoicacid (DMPA; 48.00 g), N-methyl pyrrolidone (NMP; 240.00 g),methoxypolyethylene glycol (MPEG750; 19.20 g) and polypropylene glycol(Voranol P400, trademark from Dow Europe; 618.64 g). At 50° C., toluenediisocyanate (TDI; 274.16 g) was fed into this polyol mixture while thecontents of the reactor were stirred. After the TDI feed was complete,the reaction mixture was heated to 80° C. and stirred at thistemperature for 1 hour. The resultant NCO-free urethane oligomer U2 wasthen cooled to 70° C.

A portion of this urethane oligomer (949.80 g) was diluted withdipropylene glycol monomethyl ether (97.60 g) andN,N-dimethylethanolamine (DMEA; 25.51 g) at 60° C. and the resultingmixture was stirred for 15 min at this temperature. Then hot water wasadded (50° C.; 295.25 g) and the resulting predispersion was stirred foran additional 15 min at 55 to 60° C. A portion of 1100.00 g of thismixture was subsequently fed into water (919.97 g; 50° C.) in a separatereactor over a period of 60 minutes in a nitrogen atmosphere. Aftercomplete addition, the final dispersion was stirred for an additional 15minutes at 45–50° C., then cooled to ambient temperature, filtered andstored under nitrogen. The dispersion DU2 has a solids content of 24.2%,and a pH or 7.7.

-   The viscosity of an 80% solids solution in NMP (50° C., shear rate    91.1 s⁻¹) is 57 Pa.s.-   The viscosity of a 70% solids solution in NMP/H₂O/DMEA (20/7/3) (23°    C., shear rate 91.9 s⁻¹) is 36.7 Pa.s.-   GPC analysis of U2: Mw=10,251; Mn=4,476; PDi=2.29-   Acid value of U2=20.93 mg/KOHg.    Preparation of Dispersed Vinyl Polymer P1

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer and vortex breakers was loaded with demineralised water(652.57 g), Atpol E5720/20 (4.99 g) and Borax.10H2O (3.57 g) in anitrogen atmosphere. The mixture was heated whilst stirring to 80° C.and then a solution of AP (2.31 g) in demineralised water (16.00 g) wasadded. In a dropping funnel a pre-emulsion was prepared by stirring amixture of demineralised water (161.87 g), Atpol E5720/20 (94.85 g),Aerosol OT-75 (7.20 g), Borax.10H2O (1.07 g), MMA (534.18 g), n-BA(444.32 g) and AA (19.97 g). 5% of this pre-emulsion was added to thereactor at 80° C. over 5 minutes. The remainder was fed into the reactorover 160 minutes at 85° C. A solution of AP (0.53 g) in demineralisedwater (7.88 g) was added to the reactor during the first 15 minutes offeeding the pre-emulsified feed. Then the reactor content was kept at85° C. for 30 minutes, and then cooled to ambient temperature. The pHwas adjusted to 8 to 8.5 with 12.5% aqueous ammonia. The resultantproduct (P1) was filtered and collected.

The properties of P1 are listed in Table 4.

Preparation of a Sequential Dispersed Vinyl Polymer P2

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer and vortex beakers, was loaded with demineralised water(990.94 g), SLS (30%, 0.55 g) and NaHCO₃, (4.44 g) in a nitrogenatmosphere. The mixture was heated whilst stirring to 80° C. and then asolution of AP (0.89 g) in demineralised water (5.00 g) was added. In adropping funnel a monomer mixture was prepared by stirring MMA (140.48g), n-BA (207.71 g) and AA (7.11 g). 10% of this mixture was added tothe reactor at 80° C. The remainder was fed into the reactor over aperiod of 40 minutes at 85° C. The content of a separate droppingfunnel, containing demineralised water (20.00 g), AP (0.36 g) and SLS30% (11.62 g) was added in the same time. The reactor content was keptat 85° C. for 30 minutes. A second monomer mixture was prepared in adropping funnel consisting MMA (464.91 g), n-BA (57.37 g) and AA (10.66g). The mixture was fed to the reactor after the 30 minutes period in 60minutes. The content of a separate dropping funnel, containingdemineralised water (30.00 g), AP (0.53 g) and SLS 30% (17.44 g) wasadded in the same time. The reactor content was kept at 85° C. for 45minutes and then cooled to ambient temperature. The pH was adjusted to 8to 8.5 with 12.5% aqueous ammonia. The resultant product P2 was filteredand collected.

The properties of P2 are listed in Table 4.

Preparation of Dispersed Vinyl Polymer P3

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer and vortex breakers, was loaded with demineralised water(194.50 g), Akyposal NAF (3.00 g), Borax.10H2O (1.25 g), Acetic acid(0.50 g) and Natrosol 250LR (10.00 g) in a nitrogen atmosphere. Themixture was heated whilst stirring to 60° C. and then a solution of AP(0.50 g) in demineralised water (10.00 g) was added. In a droppingfunnel a pre-emulsion was prepared by stirring with demineralised water(171.71 g), Akyposal NAF (3.00), Borax.10H2O (1.25 g), Acetic acid (0.50g) and Akyporox OP-250V (14.29 g) followed by VeoVa 10 (125.00 g) andvinyl acetate (375.00 g). 10% of this mixture was added to the reactorat 60° C. The mixture was heated whilst stirring to 80° C. The remainderwas fed into the reactor over 90 minutes at 80° C. The content of aseparate dropping funnel, containing a solution of AP (1.15 g) indemineralised water (60.00 g), was added in the same time. Then thereactor content was kept at this temperature for 120 minutes and thencooled to ambient temperature. The pH was adjusted to 8 to 8.5 with12.5% aqueous ammonia. The resultant product P3 was filtered andcollected.

The properties of P3 are listed in Table 4.

Preparation of the Dispersed Urethane Acrylic Polymer P4

Stage 1: A 1-L 3-necked round bottom flask, equipped with a stirrer anda thermometer, was loaded with NMP (100.00 g), DMPA (24.00 g), DesmodurW (152.68 g) and Priplast 3192 (223.33 g) in a nitrogen atmosphere. Thereaction mixture was heated to 55° C., tin octoate (0.05) was added andthe temperature was raised to 90–95° C. The mixture was kept at thistemperature for 1 hour before adding tinoctoate (0.05) and the mixturewas kept at 90° C. for an additional hour. The NCO-concentration of themixture was found to be 4.83%. The resulting NCO terminated urethaneprepolymer (500.05 g) (from which samples of a total weight of 10.0 gwere taken for % NCO determination, leaving 490.05 g of prepolymer) wasthen cooled to 70° C., neutralised with TEA (17.75 g) diluted with BMA(196.02 g) and homogenised for 15 minutes at 65° C.

Stage 2: A 2-L 3-necked round bottom flask, equipped with a stirrer andthermometer, was loaded with a water phase consisting of water (1045.77g) and BMA (174.00 g) in a nitrogen atmosphere. A portion of theurethane prepolymer (625.00 g) prepared in Stage 1 (at 60–65° C.) wasfed into the reactor over 1 hour, keeping the temperature of the reactorcontents below 30° C. After the feed was complete, the mixture wasstirred for an additional 5 minutes before chain-extension by theaddition of an aqueous 64.45% hydrazine hydrate solution (N₂H₄.H₂O,11.43 g in 25.00 g H₂O). A reactor temperature of 36° C. was reached.Subsequently, a 5% aqueous initiator solution of t-BHPO (18.10 g) and a1% aqueous solution of Fe^(III).EDTA; 4.63 g) was added to the reactionmixture. The radical polymerisation was started by the addition of a 1%aqueous iAA (45.24 g) and the reaction temperature was allowed to reach56° C. before more aqueous iAA (45.24 g) was added. The reaction mixturewas homogenised for 15 minutes, then cooled to room temperature,filtered over a 200-mesh sieve and collected. The properties of P4 arelisted in Table 4.

Preparation of Dispersed Vinyl Polymer P5

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer and baffles, was loaded with demineralised water (990.94 g),SLS 30% (0.55 g) and NaHCO₃ (4.44 g) in a nitrogen atmosphere. Themixture was heated whilst stirring to 80° C. and then a solution of AP(0.89 g) in demineralised water (5.00 g) was added. STY (468.54 g),2-EHA (361.69 g) and M (58.00 g) were mixed in a dropping funnel. 10% ofthis mixture was added to the reactor at 80° C. and remainder was fedinto the reactor over 100 minutes at 85° C. The content of a separatedropping funnel, containing demineralised water (50.00 g), AP (0.89 g)and SLS 30% (29.06 g) was added in the same time and the reactor contentwas kept at 85° C. for 45 minutes and then cooled to 60° C. At 60° C. aburn-up was applied by adding a solution of iAA (2.60 g) indemineralised water (49.00 g) to the reactor followed by a mixture oft-BHPO (80%,2.40 g) and demineralised water (18.00 g). After 60 minutesthe reactor content was cooled to ambient temperature. The pH wasadjusted to 8 to 8.5 with 12.5% aqueous ammonia. The product P5 wasfiltered and collected. The properties of P5 are listed in Table 4.

Preparation of Dispersed Polymers P6 to P11 and P13 and P14

The dispersed polymers P6 to P11 and P13 and P14 were prepared using themethod described for P5 with the variations as listed in Table 3. Theproperties of P6 to P11 are listed in Table 4. P13 has a weight averagemolecular weight of 22097, an Mn of 10451 and a PDi of 2.11. The Mn'sand Mw's of P1 to P12 and P14 could not be measured.

Preparation of a Fatty Acid Functional Dispersed Polymer P12

In a 1L 3-necked round bottom reactor, equipped with stirrer and N₂inlet, Nouracid LE80 (398.8 g), GMA (201.2 g), Irganox 1010 (0.10 g),Phenothiazine (0.10 g) and benzyl trimethylammonium hydroxide (40 wt %in water; 1.05 g) were loaded. The reactor was purged with nitrogen andthe yellow reaction mixture was heated and stirred at 155° C. until theacid value had dropped to 3.7 mg KOH/g. After cooling to ambienttemperature, the product was collected and stored under nitrogen.

A portion of 161.3 g of this adduct was mixed with MAA (40.3 g) andtransferred into a dropping funnel. This mixture was slowly added over aperiod of one hour to a 1L 3-necked round bottom reactor containing asolution of lauroyl peroxide (21.4 g) in butyl glycol (273.0 g) at 125°C. in a nitrogen atmosphere. After complete addition, the resultingcopolymer solution was cooled to 50° C. and subsequently concentrated invacuo to 80% solids using a rotary evaporator. To the resulting yellowsolution, a mixture of water (580.0 g), aqueous ammonia (25%; 12.0 g)and SLS (4.4 g) was added at 70° C. A mixture of MMA (225.5 g) and BA(92.5 g) was added to the resulting dispersion and the reaction mixturewas stirred for 30 minutes at 70° C. The reaction mixture was heated to85° C. and a solution of ammonium persulphate (0.86 g) in water (20.0 g)was added over a period of 10 min. The mixture was stirred at 85° C. for3 h. Then a second portion of ammonium persulphate (0.86 g) in water(20.0 g) was added and the mixture was stirred at 85° C. for 30 minutes.Then a third portion of ammonium persulphate (0.86 g) in water (20.0 g)was added and the mixture was stirred for an additional 30 minutes at85° C. The resulting dispersion was cooled to ambient temperature,filtered and stored under nitrogen. The dispersion had a solids contentof 39.3%, a pH of 7.7 and contained 2.59% butyl glycol on totaldispersion.

TABLE 3 Components (g) P6 P7 P8 P9 P10 P11 P13 P14 Reactor phase Water912.19 960.66 990.94 1001.24 960.66 990.94 1001.84 952.57 SLS 30% —72.94 0.55 — 72.94 0.55 — — Surfactant 0.83 — — — — — — 0.92 NaHCO₃ 4.124.38 4.44 4.46 4.38 4.44 4.39 4.57 Shot at 80° C. AP 0.83 0.88 0.89 0.890.88 0.89 0.88 0.92 water 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.52Monomer mixture STY — — — — — 399.70 — — MMA 577.36 332.60 617.32 352.94759.26 124.35 346.07 611.55 BA 236.86 402.63 253.15 521.85 89.76 133.24511.70 239.02 BMA — — — — — 204.29 — — AA 16.62 17.77 17.85 17.51 17.7717.51 18.29 MAA — 87.53 — — — — — — Dynasilan MEMO 41.54 — — — — — — —HEMA — 52.52 — — — — — — TEGDMA — — — — 8.75 — — — IOTG — — — — — —17.01 — AAEM — — — — — — — 45.73 Separate feed water 50.00 50.00 50.0050.00 50.00 50.00 50.00 52.50 AP 0.83 0.88 0.89 0.89 0.88 0.89 0.88 0.92SLS 30% — — 29.06 14.88 — 29.06 14.59 — Surfactant 123.79 — — — — — —136.72 P11 only = Burn-up at 60° C. with IAA (0.88 g) water (12 g) tBHPO(0.88 g) and water (26.7 g)

TABLE 4 Parameter P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 Solids[wt %] 51.2 45.1 50.3 35.2 42.4 44.6 21.4 45.0 45.0 44.6 44.3 39.3 44.544.5 pH 8.3 8.3 8.2 7.9 8.3 8.2 8.0 8.2 8.2 8.3 8.2 7.7 8.4 8.4 Particlesize [nm] 450 230 330 65 255 390 69 307 590 67 230 — 350 406 MeasuredTg*[° C.] 25 2 24 43 27 58 40 57 2 96 54 49 −7 51 Acid value** 15.6 15.60 12.4 50.6 15.6 63.4 15.6 15.6 15.6 15.6 — 15.6 15.6 *with DSC(midpoint) **Theoretical on solids [mgKOH/g]Preparation of Blends of the Dispersed Oligomers and Dispersed PolymersPrepared Above.Preparation of a Blend of Oligomer Dispersion DE1 and Dispersed PolymerP1=E1P1

In a nitrogen atmosphere, a 1-L 3-necked round bottom flask, equippedwith a stirrer, was loaded with dispersion DE1 (75.00 g) and the vinylpolymer latex P1 (38.50 g). The mixture was stirred for 30 minutes atambient temperature, filtered and then stored under nitrogen. Theresultant dispersion E1P1 had a solids content of 34.71% by weight.

The oligomer/polymer blends listed in Table 5 below were prepared usingthe method described above for E1P1.

TABLE 5 Components DE1 E1P1 E1P2 E1P3 E1P4 E2P5 Oligomer DE1 E1 E1 E1 E1E2 Oligomer (g) 130.00 75.00 75.00 75.00 75.00 100.00 Oligomer (% ofsolids) 100.00 50.00 50.00 50.00 50.00 70.00 Polymer — P1 P2 P3 P4 P5Polymer (g) — 38.50 43.70 39.20 56.00 32.10 Polymer (% of solids) —50.00 50.00 50.00 50.00 30.00 Dispersion solids % 26.3 34.7 33.2 34.530.1 34.4 pH 8.5 8.5 8.4 8.5 8.4 7.4 Components E3P6 E4P7 E5P8 E6P9E6P13 E8P8 Oligomer E3 E4 DE5 DE6 DE6 DE8 Oligomer (g) 100.00 40.0081.80 17.20 19.63 150.00 Oligomer 35.00 30.00 80.00 15.00 15.00 40.00 (%of solids) Polymer P6 P7 P7 P8 P9 P8 Polymer (g) 108.70 174.50 12.2086.50 100.00 325.00 Polymer 65.00 70.00 20.00 85.00 85.00 60.00 (% ofsolids) Additive — DPM — Water Water Water Additive (g) — 42.50 — 10.0010.00 66.67 Dispersion 35.6 20.7 40.6 40.3 40.3 45.0 solids % pH 7.6 7.78.1 8.2 8.4 8.3 Components E2U1P10 E1E3U2P11 E7P12 E7P14 OligomerDE2/DU1 DE1/DE2/DU2 DE7 DE7 Oligomer (g) 18.70/99.20 21.40/10.9/42.435.00 35.00 Oligomer 60.00 60.00 40.00 30.00 (% of solids) Polymer P10P11 P12 P14 Polymer (g) 44.80 31.80 68.50 94.20 Polymer 40.00 40.0060.00 70.00 (% of solids) Additive — — Borchersdry BG VP0133 Additive(g) — — 0.30 5.00 Dispersion 30.7 33.0 43.2 44.6 solids % pH 7.2 8.1 7.27.0

EXAMPLE 1 Pigmented Paint Composition Comprising Dispersion DE1

A 1-L 3-necked round bottom flask, equipped with a stirrer, was loadedwith dispersion DE1 (130.00 g) and TiO₂-based pigment paste (C830; 42.10g; solids content of 74.9%) in a nitrogen atmosphere, and the mixturewas stirred for 30 minutes at ambient temperature. The resulting paintformulation had a solids content of 36.8%. Then the wetting agent (Byk344; 0.1–0.2% on paint solids) and finally a urethane thickener(Borchigel L75N, Trademark from Bayer, approximately 1.5 g) was addeduntil a suitable paint-viscosity was obtained (4,000 to 6,000 mPa.s).The paint formulation was left is undisturbed for 24 h, then stirred upto mix the contents intimately, checked (and when necessary corrected)for its viscosity, and finally tested on drying and other properties.

C830 is a pigment formulation comprising TiO₂ (24.0 g), AMP-95 (0.2 g),water (3.3 g), Dehydran 1293 (0.5 g), Surfinol 104 E (0.4 g).

Paint examples 2 to 14 and 16 (and the comparative examples C6, C8 andC10) were prepared according to similar procedures using the componentspresented in Table 6. Example 17 demonstrates the use of theoligomer/polymer system used in working example 14 as a working clearcoat (i.e. non-pigmented) system. Example 15 uses an iron oxide pigmentinstead of C830. The drying and other properties of these examples arealso presented in Table 6.

The water resistance of example 14 and Example 16 before recovery was 5and after recovery was 5. The sandability of examples 7, 13 and 16 were2.5 hours, 22 hours and 18 hours respectively.

Comparative Example 18

P5 was formulated with butyl glycol (8.48 g) and the resultingdispersion was thickened with Borchigel L75N to a viscosity of 4000 to6000 mPa.s.

Comparative Example 19

P7 was used without further formulation.

TABLE 6 Example 1 2 3 4 5 6 7 Binder DE1 E1P1 E1P2 E1P3 E1P4 E2P5 E3P6Binder (g) 130.00 113.50 118.70 114.20 131.00 132.10 208.70 Pigment C830(g) 42.10 48.50 48.50 48.50 48.50 55.90 91.80 Open Time (mins) 140 30 5045 50 32 28 Wet edge time (mins) 70 17 30 18 20 17 13 Dust-free time(mins) 135 30 40 35 35 35 18 Tack-free time (h) 15 6 1.5 2 2.5 3.5 0.8Thumb-hard time (h) 24 24 6 9 6 6 2 Yellowness at start 3.69 3.49 2.783.02 2.6 2.21 1.62 Yellowing (Δb-dark) 6.07 3.77 3.16 3.46 2.94 0.160.28 Yellowing (Δb-day) 2.69 0.86 0.85 1.02 1.37 0.29 0.33 Example 8 910 11 12 13 Binder code E4P7 E5 E6 E2U1P10 E1E3U2P11 E7 Binder (g)257.00 94.00 113.70 162.70 106.60 103.80 Pigment C830 (g) 65.60 50.3056.30 61.60 43.40 55.30 Open Time (mins) 25 34 30 65 23 59 Wet edge time(mins) 12 16 18 24 15 16 Dust-free time (mins) 45 140 25 30 30 30Tack-free time (h) 2.5 18 2 3 3 1 Thumb-hard time (h) 3.5 24 6 4 6 2.5Yellowness at start 2.18 5.59 4.85 4.67 2.6 2.52 Yellowing (Δb-dark)1.47 4.22 1.27 2.61 2.27 0.77 Yellowing (Δb-day) 0.33 0.93 −0.43 1.151.12 1.58 Example 14 15 16 17 C18 C19 Binder code E7P14 E7P14 E8 E7P14P5 P7 Binder (g) 129.20 85.00 130.00 81.83 100 100 Pigment paste (g)C830 73.70 PW602, 3.0 g 72.01 — — — Open Time (mins) 52 52 42 65 35 45Wet edge time (mins) 17 16 14 27 7 8 Dust-free time (mins) 30 40 20 3015 30 Tack-free time (hours) 0.8 1.3 1.5 0.8 1.5 0.5 Thumb-hard time(hours) 1 1.5 1.5 7 2 1 Yellowness at start 2.74 — 3.39 — — — Yellowing(Δb-dark) 0.19 — 3.15 — — — Yellowing (Δb-day) 0.89 — 1.80 — — —Equilibrium Viscosity Data of the Examples Prepared Above

The equilibrium viscosity of the examples prepared above was measuredusing a number of shear rates and the results are tabulated below inTables 7 to 25.

TABLE 7 Example 1: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2.0 37.04 16 14 9 7 14.0 40.97 52 28 18 7 30.0 47.27 394 258 74 — 34.049.27 1770 456 259 — 40.0 52.32 1840 471 259 — 43.5 54.24 821 168 52 —50.0 57.7 883 178 54 — 57.0 61.9 1770 192 40 — 63.5 64.93 1700 193 42 2069.0 66.43 2080 226 47 21 76.5 67.76 1950 231 49 22

TABLE 8 Example 2 Shear rate Shear rate Shear rate Shear rate 0.0997 s⁻¹0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)7 49.8 113.0 30.2 12.2 4.6 11 51.9 171.0 43.3 15.9 5.8 16 54.4 261.051.2 17.9 5.3 18 55.4 300.0 61.6 20.1 5.0 23 57.9 359.0 64.7 17.6 4.6 3161.7 916.0 152.0 28.6 5.7 36 64.1 2640.0 389.0 60.7 — 38 65.0 2480.0358.0 47.7 — 43 67.2 5020.0 646.0 87.9 18.6 48 69.4 10200.0 2010.0 213.058.2 53 71.6 22800.0 4610.0 440.0 — 62 75.3 23700.0 4940.0 691.0 126.069 78.0 33100.0 4770.0 424.0 —

TABLE 9 Example 3: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity Viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)3.0 45.22 176 46 17 7 11.0 48.71 358 65 26 10 22.0 53.91 513 103 52 1528.5 57.22 427 159 70 — 35.0 60.69 1630 363 75 — 40.0 63.48 2460 515 — —46.0 66.95 2390 492 105 — 52.0 70.57 11100 — — —

TABLE 10 Example 4: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)1.0 45.01 126 23 11 4 7.0 47.50 113 25 13 5 13.0 50.14 235 44 22 9 17.552.21 153 52 27 11 24.0 55.36 275 104 48 19 28.0 57.39 337 134 56 — 34.060.57 1530 303 76 — 39.0 63.36 2520 482 117 — 46.0 67.48 18200 3890 285— 52.0 71.22 30800 8070 — — 57.0 74.50 28000 — — —

TABLE 11 Example 5: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity Viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)0.0 41.06 187 50 17 8 7.0 43.17 275 54 21 9 13.0 45.22 424 92 35 13 19.047.47 727 163 53 17 23.5 49.29 594 152 50 129 30.0 52.13 1920 543 122 —34.5 54.25 3160 699 165 — 40.0 56.99 6840 1030 255 — 44.0 59.09 98401520 300 — 50.0 62.42 41100 — — —

TABLE 12 Example 6 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)7 50.5 33.7 14.3 8.0 6.3 18 57.0 43.8 23.6 13.5 8.6 23 60.1 74.9 31.717.8 8.5 28 63.2 130.0 55.1 28.3 13.2 33 66.4 293.0 97.6 47.0 17.1 3970.4 871.0 186.0 84.9 48.0 44 73.8 1630.0 582.0 402.0 288.0 52 79.33060.0 1140.0 626.0 250.0 58 83.6 66200.0 — — —

TABLE 13 Example 7 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)7 50.5 382.0 51.0 22.9 12.1 13 53.2 260.0 52.0 24.5 15.6 18 55.6 1140.0106.0 49.1 16.8 23 58.2 876.0 92.2 51.8 — 28 60.9 2760.0 268.0 98.3 20.539 67.3 18300.0 3490.0 722.0 — 44 70.4 — — — — 46 71.6 13000.0 2190.0443.0 — 51 74.9 — — — —

TABLE 14 Example 8 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)6 39.4 27 17 6 2 10 40.7 49 22 7 2 19 43.9 363 90 18 — 22 45.1 854 13627 — 31 48.6 243 46 18 33 36 50.8 580 97 108 73 42 53.4 3160 1140 521 9451 57.6 2580 1790 592 108 57 60.6 3130 2770 900 323

TABLE 15 Example 9 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)3 52.5 22.5 15.2 9.4 7.8 7 54.0 34.9 20.9 13.2 10.8 15 56.8 67.3 35.721.4 17.1 18 57.8 184.0 62.4 24.1 16.6 25 59.9 115.0 47.1 25.2 18.3 2961.0 114.0 44.7 26.6 19.5 35 62.5 298.0 78.5 34.4 22.2 41 63.9 435.094.7 39.8 24.2 47 65.0 529.0 113.0 46.5 26.3 54 66.2 688.0 138.0 56.530.1 60 67.0 836.0 167.0 65.5 32.7 65 67.6 907.0 181.0 67.9 32.5 68 67.9948.0 189.0 74.0 33.8 73 68.3 1080.0 197.0 76.9 — 81 68.6 1130.0 233.091.0 36.1 93 68.6 1540.0 322.0 133.0 — 98 68.4 1530.0 334.0 133.0 — 10368.1 1680.0 344.0 134.0 — 108 67.7 1630.0 347.0 140.0 —

TABLE 16 Example 10 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)4 40.9 231.0 25.9 10.5 4.5 7 42.4 174.0 34.9 12.7 3.7 15 46.2 318.0 61.624.6 6.4 18 47.7 307.0 80.3 32.1 7.7 26 51.7 604.0 136.0 54.9 11.1 3254.7 1360.0 239.0 70.2 9.5 37 57.3 2200.0 354.0 71.3 8.0 43 60.4 9600.01040.0 — — 50 64.2 21100.0 2220.0 650.0 — 55 66.9 43500.0 8390.0 1700.0—

TABLE 17 Example 11 Shear rate Shear rate Shear rate Shear rateCalculated 0.0997 s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculatedviscosity viscosity viscosity viscosity (min) solids (%) (Pa · s) (Pa ·s) (Pa · s) (Pa · s) 3 43.64 27.6 9.2 3.7 2.0 9 45.57 32.0 17.4 5.5 2.813 46.91 72.0 21.8 7.1 3.9 19 48.99 59.0 19.3 7.8 4.4 25 51.17 111.034.1 13.4 6.2 31 53.44 201.0 48.3 19.8 7.7 36 55.41 358.0 72.9 26.9 9.144 58.69 695.0 134.0 37.2 — 49 60.82 911.0 176.0 45.5 — 54 63.02 1960.0338.0 — — 61 66.21 5150.0 768.0 — —

TABLE 18 Example 12 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)6 47.9 99.1 33.7 18.6 9.7 11 51.0 162.0 49.7 25.7 12.3 13 52.2 234.057.7 28.8 11.9 19 55.8 426.0 76.2 33.4 13.7 28 61.0 588.0 107.0 40.114.1 38 66.5 2620.0 316.0 63.5 12.1 44 69.6 13600.0 1500.0 — — 46 70.614100.0 1200.0 1510.0 51.3 53 74.1 54900.0 4740.0 152.0 118.0 58 76.570900.0 6040.0 617.0 177.0

TABLE 19 Example 13 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2 55.35 13.90 13.00 10.40 3.21 7 57.43 55.10 24.60 15.90 4.52 14 60.6292.90 41.70 24.50 — 18 62.60 170.00 36.90 27.70 7.50 25 66.32 233.0063.40 42.60 11.40 30 69.18 481.00 85.10 54.50 15.20 37 73.47 868.00152.00 75.10 41.10 41 76.07 1890.00 288.00 97.80 — 47 80.18 3310.00463.00 107.00 — 51 83.05 17000.00 2010.00 264.00 —

TABLE 20 Example 14 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2.00 56.57 33.80 11.90 5.66 6.26 7.50 59.61 44.40 15.30 7.53 4.42 14.5063.48 97.20 20.30 9.84 6.30 19.50 66.24 87.70 27.70 13.10 7.49 25.0069.28 634.00 31.30 16.30 8.93 30.00 72.04 584.00 49.20 26.30 13.10 37.0075.90 982.00 80.90 33.00 15.30 42.50 78.94 2410.00 218.00 51.90 — 49.0082.53 3240.00 208.00 65.20 23.90

TABLE 21 Example 15 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity Viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)1.00 45.34 94.90 43.10 24.00 — 1.00 45.34 135.00 54.30 28.00 5.51 10.5048.94 183.00 84.70 48.80 10.20 14.50 50.70 249.00 119.00 67.60 13.1020.00 53.36 285.00 140.00 81.90 — 24.00 55.46 470.00 219.00 107.00 —28.50 58.00 612.00 277.00 132.00 — 35.00 61.98 1020.00 448.00 178.00 —38.50 64.29 1250.00 434.00 — — 41.50 66.35 2020.00 805.00 — — 47.0070.34 2210.00 867.00 — — 51.00 73.41 4620.00 1250.00 — — 55.00 76.635760.00 1550.00 — — 61.00 81.73 17300.00 — — —

TABLE 22 Example 16 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2.00 56.54 — 30.20 10.90 4.11 6.00 58.39 213.00 41.40 13.90 4.73 12.0061.07 347.00 49.60 15.00 5.59 16.50 63.02 371.00 58.20 15.90 6.33 21.5065.10 630.00 105.00 25.40 8.83 26.00 66.92 689.00 115.00 27.60 — 32.0069.24 975.00 177.00 35.80 9.42 36.00 70.73 — 227.00 54.50 — 43.00 73.221310.00 202.00 56.80 — 49.00 75.24 1640.00 213.00 — — 55.00 77.153550.00 433.00 101.00 — 60.00 78.66 6680.00 — — — 66.00 80.37 85400.00 —— —

TABLE 23 Example 17 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2 42.43 55.00 26.10 16.40 3.64 6 43.93 76.50 35.50 19.10 4.03 10 45.1698.70 45.70 24.90 5.26 15 46.93 126.00 60.30 32.90 7.19 20 48.69 156.0076.90 41.30 8.60 25 50.76 210.00 102.00 53.70 7.31 30 53.01 210.00132.00 73.00 14.50 35 55.37 257.00 129.00 96.30 17.60 40 57.64 — 206.00127.00 10.80 45 60.32 593.00 340.00 138.00 8.50 50 63.27 1160.00 489.00184.00 9.19 55 66.53 2350.00 686.00 257.00 3.66 60 70.14 2740.00 920.00244.00 33.50 65 73.99 9100.00 1300.00 302.00 48.40

TABLE 24 Example C18 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated Viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)3.0 41.74 506 104 16 3 9.0 46.28 1465 341 59 13 14.5 50.99 5043 1334 30551 23.0 59.16 16240 5356 910 193 29.0 65.50 22290 12750 2040 448

TABLE 25 Example C19 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)0. 22.20 68 28 10 3 5.0 24.03 120 56 18 4 12.0 26.54 1156 422 82 15 18.028.93 5804 1588 212 33 24.0 31.81 8118 2073 289 69 31.0 36.13 12560 4273568 116 38.0 41.88 12720 3278 415 78 44.0 48.27 33020 8738 1087 186

1. An aqueous coating composition comprising an ambient temperaturecrosslinkable water-dispersible polyester oligomer(s) and a dispersedpolymer(s) having a measured weight average molecular weight ≧120,000Daltons where the ratio of crosslinkable polyester oligomer(s) to thedispersed polymer(s) is in the range of from 90:10 to 20:80, and from 0to 25% of co-solvent by weight of the composition, and wherein saidcomposition when drying to form a coating has the following properties:i) an open time of at least 20 minutes at 23±2° C.; ii) a wet edge timeof at least 10 minutes at 23±2° C.; iii) a thumb hard time of ≦48 hoursat 23±20° C.; iv) a tack-free time of ≦20 hours at 23±2° C.; and v) anequilibrium viscosity of ≦3,000 Pa.s, at any solids content when dryingin the range of from 20 to 55% by weight of the composition, using anyshear rate in the range of from 9±0.5 to 90±5 s⁻¹ and at 23±2° C.; andwherein the crosslinkable polyester oligomer(s) is ≦80% by weightsoluble in water throughout a pH range of from 2 to 10, and has an acidvalue in the range of from 0 to 90 mg KOH/g.
 2. An aqueous coatingcomposition comprising: i) 3 to 26% of a crosslinkable oligomer(s) byweight of the composition of which at least 52 wt % is an ambienttemperature crosslinkable water-dispersible polyester oligomer(s); ii) 0to 6.5% of a non-crosslinkable oligomer(s) by weight of the composition;iii) 10 to 56% of dispersed polymer(s) by weight of the composition,said dispersed polymer(s) having a measured weight average molecularweight ≧120,000 Daltons; iv) 0 to 25% of co-solvent by weight of thecomposition; v) 5 to 65% of water by weight of the composition; wherei)+ii)+iii)+iv)+v)=100%; and wherein said composition when drying toform a coating has the following properties: i) an open time of at least20 minutes at 23±2° C.; ii) a wet edge time of at least 10 minutes at23±2° C.; iii) a thumb hard time of ≦48 hours at 23±2° C.; iv) atack-free time of ≦20 hours at 23±2° C.; and v) an equilibrium viscosityof ≦3,000 Pa.s, at any solids content when drying in the range of from20 to 55% by weight of the composition, using any shear rate in therange of from 9±0.5 to 90±5 s⁻¹ and at 23±2° C.; and wherein thecrosslinkable polyester oligomer(s) is 80% by weight soluble in waterthroughout a pH range of from 2 to 10; and has an acid value in therange of from 0 to 90 mg KOH/g.
 3. An aqueous coating compositionaccording to claim 1 or claim 2 wherein said polyester oligomer(s) has asolution viscosity ≦250 Pa.s, as determined from a 70% by weight solidssolution of the crosslinkable polyester oligomer(s) in a solvent mixtureconsisting of: i) at least one of the solvents selected from the groupconsisting of N-methylpyrrolidone, n-butylglycol and mixtures thereof;ii) water and iii) N,N-dimethylethanolamine; where i), ii) and iii) arein weight ratios of 20/7/3 respectively, using a shear rate of 90±5 s⁻¹and at 23±2° C.
 4. An aqueous coating composition according to claim 1or claim 2 wherein said polyester oligomer(s) has a solution viscosity≦150 Pa.s, as determined from a 80% by weight solids solution of thecrosslinkable polyester oligomer(s) in at least one of the solventsselected from the group consisting of N-methylpyrrolidone, n-butylglycoland mixtures thereof, using a shear rate of 90±5 s⁻¹ and at 50±2° C. 5.An aqueous composition according to any one of claim 1 or 2 wherein saidcomposition has an equilibrium viscosity ≦5,000 Pa.s when measured usingany shear rate in the range of from 0.09±0.005 to 90±5 s⁻¹, and anequilibrium viscosity of ≦3,000 Pa.s when measured using any shear ratein the range of from 0.9±0.05 to 90±5 s⁻¹ , and an equilibrium viscosityof ≦1,500 Pa.s when measured using any shear rate in the range of from9±0.5 to 90±5 s⁻¹, at any solids content when drying in the range offrom 20 to 55% by weight of the composition and at 23±2° C.
 6. Anaqueous composition according to any one of claim 1 or 2 wherein saidcomposition has an equilibrium viscosity ≦5,000 Pa.s when measured usinga shear rate in the range of from 0.09±0.005 to 90±5 s⁻¹ after a 12%increase of the solids content by weight of the composition when drying.7. An aqueous composition according to any one of claim 1 or 2 whereinthe crosslinkable polyester oligomer(s) has a measured weight averagemolecular weight in the range of from 1,000 to 100,000 Daltons.
 8. Anaqueous composition according to any one of claim 1 or 2 wherein thecrosslinkable polyester oligomer(s) has a PDi≦30.
 9. An aqueouscomposition according to any one of claim 1 or 2 wherein thecrosslinkable polyester oligomer(s) has a measured Tg in the range offrom −90 to 100° C.
 10. An aqueous composition according to any one ofclaim 1 or 2 wherein the crosslinkable water-dispersible polyesteroligomer(s) is self-crosslinkable.
 11. An aqueous composition accordingto any one of claim 1 or 2 wherein the crosslinkable water-dispersiblepolyester oligomer(s) is crosslinkable by autoxidation optionally incombination with Schiff base crosslinking.
 12. An aqueous compositionaccording to claim 11 wherein the crosslinkable water-dispersiblepolyester oligomer(s) contains autoxidisable groups and carbonylfunctional groups.
 13. An aqueous composition according to any one ofclaim 1 or 2 wherein the crosslinkable water-dispersible polyesteroligomer(s) is crosslinkable by Schiff base crosslinking optionally incombination with silane condensation.
 14. An aqueous compositionaccording to any one of claim 1 or 2 wherein the crosslinkablewater-dispersible polyester oligomer(s) is crosslinkable by silanecondensation optionally in combination with autoxidation.
 15. An aqueouscomposition according to claim 1 or claim 2 wherein the dispersedpolymer(s) has particle size in the range of from 25 to 1000 nm.
 16. Anaqueous composition according to claim 1 or claim 2 wherein thedispersed polymer(s) has an acid value below 150 mgKOH/g.
 17. An aqueouscomposition according to claim 1 or claim 2 wherein the dispersedpolymer(s) is a vinyl polymer.
 18. An aqueous composition according toclaim 17 wherein the dispersed polymer(s) has a measured Tg in the rangeof from −50 to 300° C.
 19. An aqueous coating composition according toclaim 1 or claim 2 comprising: i) 0 to 15% co-solvent by weight ofcrosslinkable oligomer(s), non-crosslinkable oligomer(s) and dispersedpolymer(s); ii) 35 to 65% of crosslinkable polyester oligomer(s) byweight of crosslinkable oligomer(s), non-crosslinkable oligomer(s) anddispersed polymer(s); wherein the crosslinkable polyester oligomer(s)comprises 45 to 75 wt % of fatty acid groups; and wherein the dispersedpolymer(s) has an acid value below 20 mgKOH/g.
 20. An aqueous coatingcomposition according to any one of claim 1 or 2 additionally comprisinga pigment.
 21. A substrate having a coating obtained from an aqueouscomposition according to any one of claim 1 or
 2. 22. An aqueous coatingcomposition comprising an ambient temperature crosslinkablewater-dispersible polyester oligomer(s) and a dispersed polymer(s)having a measured weight average molecular weight <120,000 Daltons wherethe ratio of crosslinkable polyester oligomer(s) to the dispersedpolymer(s) is in the range of from 90:10 to 20:80, and from 0 to 25% ofco-solvent by weight of the composition, and wherein said compositionwhen drying to form a coating has the following properties: i) an opentime of at least 20 minutes at 23±2° C.; ii) a wet edge time of at least10 minutes at 23±2° C.; iii) a thumb hard time of ≦48 hours at 23±2° C.;iv) a tack-free time of ≦20 hours at 23±2° C.; and v) an equilibriumviscosity of ≦3,000 Pa.s, at any solids content when drying in the rangeof from 20 to 55% by weight of the composition, using any shear rate inthe range of from 9±0.5 to 90±5 s⁻¹ and at 23±2° C.; and; wherein thecrosslinkable polyester oligomer(s) is ≦80% by weight soluble in waterthroughout a pH range of from 2 to 10, and has an acid value in therange of from 0 to 90 mg KOH/g with the proviso that the dispersedpolymer(s) is a vinyl polymer and has a solid viscosity >150 Pa.s, asdetermined from an 80% by weight solids solution of the dispersedpolymer(s) in at least one of the solvents selected from the groupconsisting of N-methylpyrrolidone, n-butylglycol and mixtures thereof,using a shear ate of 90±5 s⁻¹ and at 50±2° C.
 23. An aqueous coatingcomposition comprising an ambient temperature crosslinkablewater-dispersible polyester oligomer(s) and a dispersed polymer(s)having a measured weight average molecular weight <120,000 Daltons wherethe ratio of crosslinkable polyester oligomer(s) to the dispersedpolymer(s) is in the range of from 90:10 to 20:80, and from 0 to 25% ofco-solvent by weight of the composition, and wherein said compositionwhen drying to form a coating has the following properties: i) an opentime of at least 20 minutes at 23±2° C.; ii) a wet edge time of at least10 minutes at 23±2° C.; iii) a thumb hard time of ≦48 hours at 23±2° C.;iv) a tack-free time of ≦20 hours at 23±2° C.; and v) an equilibriumviscosity of ≦3,000 Pa.s, at any solids content when drying in the rangeof from 20 to 55% by weight of the composition, using any shear rate inthe range of from 9±0.5 to 90±5 s⁻¹ and at 23±2° C.; and; wherein thecrosslinkable polyester oligomer(s) is ≦80% by weight soluble in waterthroughout a pH range of from 2 to 10, and has an acid value in therange of from 0 to 90 mg KOH/g with the proviso that the dispersedpolymer(s) has a solution viscosity ≧250 Pa.s, as determined from an 80%by weight solids solution of the dispersed polymer(s) in at least one ofthe solvents selected from the group consisting of N-methylpyrrolidone,n-butylglycol and mixtures thereof, using a shear rate of 90±5 s⁻¹ andat 50±2° C. and with the further proviso that the crosslinkablewater-dispersible polyester oligomer(s) is selected from the groupconsisting of such polyester oligomer(s) that are self-crosslinkable,crosslinkable by autooxidation, crosslinkable by Schiff basecrosslinking or crosslinkable by silane condensation and with thefurther proviso that said polyester oligomer(s) has a solution viscosity≦150 Pa.s, as determined from a 80% by weight solids solution of thecrosslinkable polyester oligomer(s) in at least one of the solventsselected from the group consisting of N-methylpyrrolidone, n-butylglycoland mixtures thereof, using a shear rate of 90±5 s⁻¹ and at 50±2° C. 24.An aqueous coating composition comprising: i) 14 to 40% of ambienttemperature crosslinkable water-dispersible oligomer(s) by weight ofcrosslinkable oligomer(s), non-crosslinkable oligomer(s) and dispersedpolymer(s) of which at least 52 wt % is crosslinkable polyesteroligomer(s); ii) 0 to 10% of a non-crosslinkable oligomer(s) by weightof crosslinkable oligomer(s), non-crosslinkable oligomer(s) anddispersed polymer(s); iii) 50 to 85% of dispersed polymer(s) by weightof crosslinkable oligomer(s), non-crosslinkable oligomer(s) anddispersed polymer(s); said dispersed polymer(s) having a measured weightaverage molecular weight ≧120,000 Daltons and where i)+ii)+iii)=100%,and iv) 0 to 25% of co-solvent by weight of the composition, saidcomposition when drying to form a coating having the followingproperties: i) an open time of at least 20 minutes at 23±2° C.; ii) awet edge time of at least 10 minutes at 23±2° C.; iii) a thumb hard timeof ≦48 hours at 23±2° C.; iv) a tack-free time of ≦20 hours at 23±2° C.;and v) an equilibrium viscosity of ≦3,000 Pa.s, at any solids contentwhen drying in the range of from 20 to 55% by weight of the composition,using any shear rate in the range of from 9±0.5 to 90±5 s⁻¹ and at 23+2°C.; and wherein the crosslinkable polyester oligomer(s) is ≦80% byweight soluble in water throughout a pH range of from 2 to 10, and hasan acid value in the range of from 0 to 90 mg KOH/g.
 25. An aqueouscoating composition comprising: i) 3 to 26% of a crosslinkableoligomer(s) by weight of the composition of which at least 52 wt % is anambient temperature crosslinkable water-dispersible polyesteroligomer(s); ii) 0 to 6.5% of a non-crosslinkable oligomer(s) by weightof the composition; iii) 10 to 56% of dispersed polymer(s) by weight ofthe composition, said dispersed polymer(s) having a measured weightaverage molecular weight <120,000 Daltons; iv) 0 to 25% of co-solvent byweight of the composition; v) 5 to 65% of water by weight of thecomposition; where i)+ii)+iii)+iv)+v)=100%; and wherein said compositionwhen drying to form a coating has the following properties: i) an opentime of at least 20 minutes at 23±2° C.; ii) a wet edge time of at least10 minutes at 23±2° C.; iii) a thumb hard time of ≦48 hours at 23±2° C.;iv) a tack-free time of ≦20 hours at 23±2° C.; and v) an equilibriumviscosity of ≦3,000 Pa.s, at any solids content when drying in the rangeof from 20 to 55% by weight of the composition, using any shear rate inthe range of from 9±0.5 to 90±5 s⁻¹ and at 23±2° C.; and wherein thecrosslinkable polyester oligomer(s) is 80% by weight soluble in waterthroughout a pH range of from 2 to 10, and has an acid value in therange of from 0 to 90 mg KOH/g with the proviso that the dispersedpolymer(s) is vinyl polymer and has a solution viscosity >150 Pa.s, asdetermined from an 80% by weight solids solution of the dispersedpolymer(s) in at least one of the solvents selected from the groupconsisting of N-methylpyrrolidone, n-butylglycol and mixtures thereof,using a shear rate of 90±5 s⁻¹ and at 50±2° C.
 26. An aqueous coatingcomposition comprising: i) 3 to 26% of a crosslinkable oligomer(s) byweight of the composition of which at least 52 wt % is an ambienttemperature crosslinkable water-dispersible polyester oligomer(s); ii) 0to 6.5% of a non-crosslinkable oligomer(s) by weight of the composition;iii) 10 to 56% of dispersed polymer(s) by weight of the composition,said dispersed polymer(s) having a measured weight average molecularweight ≧120,000 Daltons; iv) 0 to 25% of co-solvent by weight of thecomposition; v) 5 to 65% of water by weight of the composition; wherei)+ii)+iii)+iv)+v)=100%; and wherein said composition when drying toform a coating has the following properties: i) an open time of at least20 minutes at 23±2° C.; ii) a wet edge time of at least 10 minutes at23±2° C.; iii) a thumb hard time of ≦48 hours at 23±2° C.; iv) atack-free time of ≦20 hours at 23±2° C.; and v) an equilibrium viscosityof ≦3,000 Pa.s, at any solids content when drying in the range of from20 to 55% by weight of the composition, using any shear rate in therange of from 9±0.5 to 90±5 s⁻¹ and at 23±2° C; and wherein thecrosslinkable polyester oligomer(s) is ≦80% by weight soluble in waterthroughout a pH range of from 2 to 10, and has an acid value in therange of from 0 to 90 mg KOH/g with the proviso that the dispersedpolymer(s) has a solution viscosity ≧250 Pa.s, as determined from an 80%by weight solids solution of the dispersed polymer(s) in at least one ofthe solvents selected from the group consisting of N-methylpyrrolidone,n-butylglycol and mixtures thereof, using a shear rate of 90±5 s⁻¹ andat 50±2° C. and with the further proviso that the crosslinkablewater-dispersible polyester oligomer(s) is selected from the groupconsisting of such polyester oligomer(s) that are self-crosslinkable,crosslinkable by autooxidation, crosslinkable by Schiff basecrosslinking or crosslinkable by silane condensation and with thefurther proviso that said polyester oligomer(s) has a solution viscosity≦150 Pa.s, as determined from a 80% by weight solids solution of thecrosslinkable polyester oligomer(s) in at least one of the solventsselected from the group consisting of N-methylpyrrolidone, n-butylglycoland mixtures thereof, using a shear rate of 90±5 s⁻¹ and at 50±2° C.